Tools
Tools for running and growing a business online.
Calculators, converters and generators that do the job properly. No sign-up and no email address, and every one of them works on the first click.
DartvelA free framework for building apps for web, phone and desktop from one Dart and Flutter codebase, with a backend, database, sign-in and a no-code Studio built in.Web · Free.htaccess generatorBuild the Apache config for HTTPS, www, redirects, caching, compression and security headers — without a syntax error.WebA/B test significance calculatorProFind out whether your test result is real or noise, using the same two-proportion test statisticians use.BusinessAccessibility (WCAG) readinessProCheck a product against the WCAG criteria that fail real audits — and that increasingly appear in procurement.DesignAd budget plannerWork backwards from a revenue target to the ad budget, clicks and conversions you need.MarketingAd spend and ROAS calculatorWork out return on ad spend, cost per click and cost per acquisition, and the break-even you need.MarketingAdSense readiness checkerProEnter your address and we fetch the site, run the checks Google's reviewers apply, and hand back a prioritised fix list.MarketingAge calculatorWork out an exact age in years, months and days, and when the next birthday falls.DataAPI rate limit and quota plannerProSize rate limits and quotas for an API product so real customers are not throttled and abuse still is.DeveloperAspect ratio calculatorResize while keeping proportions, and find the ratio of any width and height.DesignAutomation and robotics ROIProCompare a robot or automated system against the labour it replaces, honestly — including the work it cannot do.BusinessAviation seat-mile costWork out cost per available seat mile, break-even load factor and what a route actually earns.BusinessBase64 encoder and decoderEncode text to Base64 or decode it back, with URL-safe output for tokens and query strings.DeveloperBattery, range and charging calculatorConvert battery capacity into real range, charge time and cost per mile for a vehicle or device.DataBill splitterSplit a bill between people, with a tip and optional uneven shares.BusinessBillable utilisation and matter profitabilityFor firms billing time: work out utilisation, realisation and what each matter actually earns.BusinessBlockchain transaction cost calculatorWork out gas costs at different network conditions, and what an on-chain feature costs at volume.DeveloperBreak-even calculatorFind how many units you must sell to cover your fixed costs, and what that is worth in revenue.BusinessBulk URL slug generatorTurn a list of titles into URL slugs in one go, and flag any that collide.MarketingBurn multiple and capital efficiencyProHow many pounds you burn for each pound of new recurring revenue — and what that says about your next round.BusinessBusiness schema generatorGenerate the hidden code that tells Google your opening hours, phone number and location.MarketingCampaign link builderBuild tagged links so you can finally tell which post, ad or email actually brought the customer in.MarketingCanonical and meta robots generatorGenerate canonical tags and robots directives correctly — the tags most often set the wrong way round.MarketingCarbon removal cost per tonneWork out the real cost of removing a tonne of CO2, including the energy the process itself consumes.BusinessCard, IBAN and ISBN validatorCheck a card number, bank IBAN or ISBN is internally valid before it causes a failed payment or a bad record.BusinessCase converterConvert text between sentence case, title case, camelCase, snake_case, kebab-case and more.TextCash runway and burn rateProHow many months of cash you have left at the current burn, and what it takes to reach break-even.BusinessCharacter frequency counterCount how often each character appears — for ciphers, data cleaning and spotting stray symbols.TextChurn and retention calculatorTurn a monthly churn rate into what it actually means: annual loss, average lifetime and revenue at risk.BusinessClinical trial cost per patientProBuild up the cost of a trial by site and patient, and see what a slow-enrolling site really costs.BusinessCloud hosting cost estimatorProAdd up compute, storage and the egress bill that surprises people, and compare reserved against on-demand.BusinessCloud workload carbon estimatorEstimate the emissions of your compute, for a sustainability report or a customer questionnaire.DataCohort retention curveProTurn raw cohort counts into a retention curve, and see whether it flattens — the difference between a business and a leaky bucket.BusinessColour blindness simulatorSee how a palette looks to the 1 in 12 men with colour vision deficiency — and whether it still works.DesignColour contrast checkerCheck text and background against WCAG AA and AAA — the accessibility test most sites quietly fail.DesignColour converterConvert a colour between HEX, RGB and HSL, and get the CSS for each.DesignColour palette generatorBuild a harmonious palette from one colour: complementary, triadic, analogous and a full tint scale.DesignCompound interest calculatorProject savings or investment growth, including regular contributions, and see what is growth and what is yours.BusinessConstruction cost and contingencyBuild up a project cost with preliminaries, fees and a contingency sized to the stage you are actually at.BusinessConversion rate and funnel calculatorWork out conversion at each step of a funnel and find where you lose the most people.MarketingCost per kilogram to orbitCompare launch economics: cost per kilogram, payload utilisation and what reuse actually changes.DataCourse completion and learner funnelFind where learners drop out, what completion is worth, and which step to fix first.BusinessCron expression explainerRead a cron schedule back in plain English, so you know when it will actually run.DeveloperCSS box shadow generatorDesign a box shadow visually and copy the CSS, including multi-layer shadows that look natural.DesignCSS formatterTurn a minified or hand-mangled stylesheet back into something you can read and edit.DeveloperCSS gradient generatorBuild a linear or radial CSS gradient and copy the code, with a live preview.DesignCSS minifierStrip comments and whitespace out of CSS and see how much smaller it gets.DeveloperCSV column extractorPull out, reorder or drop columns from a CSV without opening a spreadsheet.DeveloperCSV to JSON converterTurn a spreadsheet export into JSON, handling quoted fields and embedded commas properly.DeveloperCustomer acquisition cost and lifetime valueProWork out what a customer costs to win, what they are worth, and whether that ratio is sustainable.BusinessData format converterProConvert tabular data between CSV, TSV, JSON, XML, HTML tables, Markdown tables and YAML — any format in, any format out.DataData size converterConvert between bytes, kilobytes, mebibytes and the rest — and see why your 1 TB drive shows as 931 GB.DataDatabase connection pool sizerSize a Postgres connection pool from your instance count and worker counts — and spot when you have oversubscribed it.DeveloperDate difference calculatorCount the days, weeks, months and working days between two dates.DataDAU, MAU and stickiness calculatorWork out engagement, session economics and what your stickiness ratio says about the product.BusinessDays sales outstanding calculatorMeasure how long customers actually take to pay, and what tightening that up frees in cash.BusinessDepreciation calculatorWrite an asset down over its life, straight line or reducing balance, year by year.BusinessDiscount and sale price calculatorWork out a sale price, the saving, and what a discount does to your margin before you commit to it.BusinessDORA metrics scorecardProScore your delivery on the four keys — deploy frequency, lead time, restore time and change failure rate.DeveloperDownload and transfer time calculatorHow long a file takes to transfer at a given connection speed — and where the megabit/megabyte confusion bites.DataDuplicate and overlap finderCompare two lists and see what is in both, what is only in one, and what is duplicated.DeveloperEmail address validatorCheck an address is actually valid, spot the typo, and flag disposable and role accounts.WebEmail subject line testerCheck a subject line for length, spam triggers and the things that actually suppress open rates.MarketingEmail, URL and phone extractorPull every email address, link, phone number or figure out of a block of messy text.TextEquity vesting scheduleSee exactly what vests and when, with a cliff, and what is left if someone leaves on a given date.BusinessExperiment duration calculatorProWork out how long an A/B test must run to detect the effect you care about — before you start it.MarketingFavicon generatorProTurn any image into the full set of favicon sizes, plus the HTML to drop into your head.DesignFind and replaceReplace text across many lines at once, with optional regular expressions and case sensitivity.TextFleet unit economicsProWork out whether each vehicle, scooter, robot or drone pays for itself — per unit, per day.BusinessFood and CPG unit economicsWork out margin per unit through the whole chain — ingredients, packaging, spoilage, distributor and retailer.BusinessFreelance hourly rate calculatorWork backwards from the salary you want to the rate you must charge, once unpaid time is honest.BusinessFreight cost per mileWork out what a truck actually costs to run per mile, and what empty miles are doing to the margin.BusinessFunding round dilution calculatorProSee exactly what a round leaves you owning, including the option pool top-up investors usually ask for.BusinessGDPR readiness scorecardCheck whether you can honestly answer a data protection questionnaire before a customer sends you one.BusinessGoogle and social previewSee how your page title and description will look in Google results and when shared, before you publish.MarketingGrowth rate (CAGR) calculatorTurn a start and end figure into the compound annual growth rate, and project it forward.BusinessHardware cost and margin at volumeProProject what a device costs at 1,000 units versus 100,000, using the learning curve manufacturers actually see.BusinessHash generatorGenerate MD5, SHA-1, SHA-256, SHA-384 and SHA-512 hashes of any text, in your browser.DeveloperHIPAA readiness scorecardProCheck whether a health product can handle patient data lawfully — before a hospital, insurer or investor asks.BusinessHMAC signature generatorGenerate an HMAC signature for webhook verification and signed API requests.DeveloperHreflang tag generatorProGenerate the hreflang tags that tell Google which language and region each version of a page serves.MarketingHTML entity encoderEscape characters that break HTML, or decode entities back into readable text.TextHTML formatter and minifierIndent messy HTML so you can read it, or strip it down so it ships smaller.DeveloperHTML to plain textStrip the tags out of HTML and get readable plain text, with paragraphs and line breaks kept.TextHTTP status code referenceLook up what an HTTP status code means and what you should actually do about it.WebImage resizer and converterProResize, compress and convert images to WebP, JPEG or PNG — entirely in your browser, nothing uploaded.DesignInventory turnover and cash cycleSee how long your money sits in stock, and what the cash conversion cycle is really costing you.BusinessInvestment appraisal — NPV and IRRProJudge a project properly: net present value, internal rate of return and discounted payback.BusinessInvestment performance statisticsCalculate Sharpe, Sortino, volatility and maximum drawdown from a series of returns.BusinessInvoice and quote calculatorTotal up line items with tax, a discount and a deposit, and see exactly what is due now.BusinessInvoice due date calculatorWork out when an invoice is actually due under net terms, end-of-month terms or a fixed number of days.BusinessJavaScript formatter and minifierIndent unreadable JavaScript, or strip the comments and whitespace out of it.DeveloperJSON formatter and validatorFormat, validate and minify JSON, with the exact position of any syntax error.DeveloperJSON to CSV converterFlatten an array of JSON objects into a CSV you can open in Excel or Google Sheets.DeveloperJWT decoderDecode a JSON Web Token to read its header and claims, and see whether it has expired.DeveloperKeyword density checkerSee which words and phrases dominate a page, and whether anything is repeated suspiciously often.TextLanded cost and shipping calculatorWork out what an imported unit really costs once freight, duty, tax and handling are in.BusinessLate payment interest calculatorWork out the statutory interest owed on an overdue invoice, day by day.BusinessLevelised cost of energy (LCOE)ProCompare generation technologies on the only basis that is fair: lifetime cost per megawatt-hour produced.BusinessLine break and whitespace cleanerFlatten text copied out of a PDF, collapse double spaces and strip trailing whitespace.TextList to SQL, JSON or CSVTurn a pasted column into a quoted SQL IN clause, a JSON array or a delimited line.DeveloperLLM API cost calculatorProWork out what an AI feature costs per request, per user and per month — including what prompt caching saves.BusinessLoan repayment calculatorSee the monthly payment on a loan and, more importantly, what it costs you in total interest.BusinessMarkdown to HTMLConvert Markdown into clean HTML you can paste into a CMS or an email template.TextMarketplace liquidity checkerMeasure whether your two sides actually clear — the single thing that decides if a marketplace works.BusinessMarketplace take rate and unit economicsProModel GMV, take rate and what actually reaches you after payments, support and incentives on both sides.BusinessMeeting cost calculatorPut a figure on a recurring meeting — salary cost per hour, per occurrence, and per year.BusinessMileage and fuel cost calculatorWork out what a journey actually costs in fuel, and what you can claim back per mile or kilometre.BusinessNumber base converterConvert a number between binary, octal, decimal and hexadecimal, in both directions.DeveloperNumber to words converterSpell out a number in English — for cheques, contracts and invoices.DataOccupancy and RevPAR calculatorFor hotels, short lets and flexible workspace: occupancy, ADR, RevPAR and what each unit contributes.BusinessOn-call load and alert fatigueCheck whether a rota is humane and whether your alerts are worth waking someone for.DeveloperOpen Graph and Twitter card generatorGenerate the meta tags that control how your page looks when it is shared on social media.MarketingPassword generatorGenerate strong random passwords or passphrases, with a real estimate of how long they resist cracking.DeveloperPassword strength checkerTest how long a password would resist an offline attack, entirely in your browser.WebPayment processing fee calculatorWork out what you actually net after processor fees, currency conversion and chargebacks.BusinessPayment schedule builderSplit a project fee into a deposit and milestones, and see exactly what is invoiced when.BusinessPercentage calculatorEvery percentage question in one place: X% of Y, what percent, percentage change, and reverse percentages.BusinessPlaceholder text generatorGenerate lorem ipsum paragraphs, sentences or words for mock-ups and layout testing.TextProfit margin and markup calculatorWork out margin, markup and profit from cost and price — and stop confusing the two.BusinessProperty yield and cap rate calculatorWork out gross yield, net yield, cap rate and cash-on-cash return on a property, with the costs people forget.Businesspx, rem and em converterConvert between pixels, rem, em and points against your root font size.DesignQuantum error correction overheadWork out how many physical qubits a fault-tolerant algorithm needs, using surface-code scaling.DataQuery string parserBreak a URL into its parts and read every query parameter as a table.DeveloperQueue and throughput calculatorWork out waiting times and how many servers, tills or agents you need — and why 90% utilisation feels broken.DataR&D milestone runway plannerProFor deep tech and biotech: plan spend against milestones and see which one you can actually reach on this cash.BusinessRandom number and pickerDraw random numbers, shuffle a list or pick winners fairly — with a cryptographic random source.DataReadability checkerScore your writing for reading age, and find the sentences making it hard work.MarketingRecycling and material recovery valueWork out what recovered material is worth against the cost of recovering it, and where the margin sits.BusinessRedirect map generatorTurn a list of old and new URLs into redirect rules for Apache, Nginx or a Next.js config.DeveloperRegular expression testerTest a regular expression against sample text and see every match and capture group.DeveloperRobots.txt generatorGenerate the file that tells search engines what to crawl, including the AI crawlers you may want to block.MarketingROI and payback calculatorJudge whether a spend paid for itself: return on investment, payback period and annualised return.BusinessRoman numeral converterConvert numbers to Roman numerals and back, with proper validation of malformed numerals.DataSaaS metrics calculatorProTurn one month of movements into NRR, gross churn, quick ratio and the Rule of 40 — the numbers investors ask for.BusinessSalary and hourly rate converterConvert between annual salary, monthly pay, day rate and hourly rate, both directions.BusinessSales commission calculatorWork out commission on flat or tiered rates, including accelerators above target.BusinessSecurity incident cost estimatorModel what a breach would actually cost you — detection, response, notification, churn and the fine.BusinessSLO error budget calculatorConvert a reliability target into a budget of failed requests, and see how fast you are spending it.DeveloperSOC 2 readiness scorecardProScore how close you are to passing a SOC 2 Type II audit — the thing blocking your first enterprise deal.BusinessSocial and ad character counterCheck one piece of copy against every platform limit at once, from a tweet to a Google Ads headline.MarketingSolar payback calculatorWork out when a solar installation pays for itself, and what it returns over its life.BusinessSort and deduplicate linesSort lines alphabetically or by length, reverse them, and strip duplicates or blank lines.TextSQL formatterFormat a one-line query into something readable, with the major clauses on their own lines.DeveloperStatistics calculatorMean, median, mode, standard deviation and quartiles from a list of numbers.DataStock reorder point calculatorWork out when to reorder and how much to hold, so you neither run out nor tie up cash in a warehouse.BusinessSubsidised hardware payback calculatorProWhen you sell a device below cost to win a subscription, work out when it turns profitable — and what churn does to that.BusinessSupport team staffing calculatorWork out how many support staff a ticket volume needs, what it costs per ticket, and what deflection is worth.BusinessTechnical debt interest calculatorPut a number on what deferred work costs every sprint, and when paying it down breaks even.DeveloperTelemetry and time-series storage plannerProSize the storage and cost of sensor, device or metric data before you switch the fleet on.DeveloperTemperature converterConvert between Celsius, Fahrenheit and Kelvin, with the reference points that matter.DataText comparisonCompare two versions of a text line by line and see exactly what was added and removed.TextText reverserReverse text by character, by word or by line — useful for testing and for puzzles.TextText, hex and binary converterConvert text to hexadecimal, binary or decimal byte values, and back again.DeveloperTime duration calculatorAdd up hours and minutes, work out elapsed time, and convert a total into decimal hours for invoicing.DataTime zone converterSee what a given time is in other parts of the world, using real time zone rules including DST.DataToken and context window estimatorEstimate how many tokens a document uses and whether it fits a model's context window.DeveloperTraffic capacity plannerProWork out how many instances a launch needs from your request rate and response time, using Little's Law.DeveloperTrue cost of an employeeSalary is rarely the real number — add employer contributions, benefits, equipment and holiday cover.BusinessUnit converterConvert length, weight, volume, area, speed and data sizes, with exact conversion factors.DataUnix timestamp converterConvert between Unix timestamps and human dates, in seconds or milliseconds, UTC or local.DeveloperUptime and SLA calculatorTurn an uptime percentage into the downtime it actually permits — per day, month and year.BusinessURL encoder and decoderPercent-encode text for use in a URL, or decode an encoded URL back to something readable.DeveloperURL slug generatorTurn a headline into a clean, lowercase URL slug with accents folded and punctuation removed.TextUsage-based pricing modellerProModel tiered or per-unit pricing against real customer usage, and find where your margin breaks.BusinessUUID generatorGenerate cryptographically random version 4 UUIDs, one or a thousand at a time.DeveloperVAT and sales tax calculatorAdd tax to a net price or pull it back out of a gross one — the direction people most often get wrong.BusinessViral coefficient and referral growthWork out your k-factor, whether referral alone sustains growth, and what a referral programme is actually worth.MarketingVulnerability SLA and backlog plannerProTurn a CVSS backlog into remediation deadlines and see whether your team can actually clear it.DeveloperWarehouse pick and pack throughputSize a fulfilment operation: pickers needed, cost per order, and where automation starts to pay.BusinessWhat slow pages cost youPut a number on it: estimate the orders and revenue a slow-loading site loses you every month.BusinessWord and character counterCount words, characters, sentences and paragraphs, with a reading time and a readability score.TextWorking day calculatorAdd or subtract working days from a date, skipping weekends and any holidays you list.DataXML entity encoderEscape the five characters XML reserves, or decode entities back to text.TextXML formatter and validatorBeautify, minify or strip XML, and find the tag that never closes.DeveloperXML sitemap generatorProTurn a list of URLs into a valid XML sitemap, with priorities and change frequencies.Marketing