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400+ calculators · formulas explained

Free online calculators with formulas and worked examples.

Search finance, health, math, construction and everyday tools. Get instant results with formulas, units and worked examples you can verify.

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14 focused categories

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Choose a focused collection and reach the right tool faster, from everyday calculations to specialist work.

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14focused categories
400+free tools

Every collection is organized around a clear task, with direct access to its calculators.

FinancialLoans, mortgages, savings and tax estimates 102 tools MathPercentages, algebra, geometry and statistics 45 tools HealthBMI, nutrition, fitness and wellness estimates 40 tools Date & TimeAge, duration, workdays and time zones 19 tools ConvertersUnits, currency, measurements and data 22 tools BusinessPricing, payroll, margins and growth 51 tools EducationGrades, GPA, study planning and scores 16 tools ConstructionConcrete, roofing, materials and layouts 19 tools EngineeringElectrical, HVAC and mechanical calculations 24 tools LifestyleTravel, cooking, household and daily planning 31 tools Document ToolsPDF, image and everyday document utilities 24 tools Developer ToolsGenerators, encoders and web utilities 24 tools NetworkingSubnets, bandwidth, IP and transfer tools 8 tools PhysicsMotion, energy, force and waves 16 tools
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Included with every calculator

Clear answers, by design

No account and no hidden steps. Each tool is fast, transparent about its method, and designed to respect your privacy.

  • No sign-up neededOpen any tool and calculate immediately.
  • Privacy by designMost calculations run locally in your browser.
  • Works offline once loadedMany standard tools remain usable without a connection.
  • Instant resultsSee answers update as you change the inputs.
  • Transparent formulasReview the method, assumptions and units used.
  • Designed for mobileComfortable controls and readable results on smaller screens.
See how we build and verify calculators →
Before you start

Common questions

What the numbers mean, where they come from, and what happens to what you type.

Do you store the numbers I enter?

No. Calculations run in your browser and nothing you type leaves the page — not your salary, not your loan balance, not your weight. A few tools fetch a live price (gold, currency) from a named third party, and that request sends nothing about you. Full detail in our privacy policy.

Do I need an account to use anything?

No, and there isn’t one to make. Every calculator is fully usable the moment the page loads — no sign-up, no email, no trial, no feature held back behind a login. If a site asks you to register before showing you a number, it is selling something other than the number.

How do the calculators work offline?

Because the maths runs on your device rather than a server. Once a page has loaded, it keeps working with no connection — useful on a building site, in a basement, or on a plane. The only exceptions are tools that need a live market price, which will tell you plainly when they cannot reach it.

Why do you show the formula?

So you can check the answer instead of trusting it. Every tool shows the working with your own figures substituted, plus a worked example. If a result looks wrong, you can see exactly which step produced it — which also means you learn something, rather than just collecting a number.