Free Online Calculators
for Real Decisions.
Last updated: April 2025
All calculators are free, work instantly in your browser, and require no account or sign-up. Every tool includes a plain-English explanation of the maths behind it — so you understand the result, not just get a number.
16 free calculators covering personal finance, health, and time. No sign-up. Instant results. Works in any browser.
Monthly repayments, total interest, true borrowing cost.
Monthly payment and total cost for any fixed-rate loan.
Monthly target to reach any savings goal by any date.
Take-home pay after income tax and National Insurance 2025/26.
Add or remove VAT at any rate instantly.
Fund target, 4% rule, and monthly contribution needed.
Snowball vs avalanche. Debt-free date with extra payments.
Purchasing power of money over any time period.
Three modes: of, is, and percentage change.
GBP, USD, EUR and 12 more currencies.
Restaurant tipping for USA, UK and Europe.
Free online calculators — no sign-up, no ads behind paywalls
Every calculator on SimplyCalc is completely free, works instantly in your browser, and keeps no record of the numbers you enter. There is no account to create, no email address required, and no data sent to a server. The calculations run entirely in your browser.
Finance calculators
Our finance tools cover the most common personal finance calculations: mortgage repayments for UK, USA, and European buyers; take-home pay after income tax and National Insurance for the 2025/26 tax year; VAT calculations for adding or removing UK and EU VAT; retirement planning using the 4% rule; debt payoff schedules with snowball and avalanche methods; and an inflation calculator to understand purchasing power changes over time.
Health calculators
The health tools include a BMI calculator in metric and imperial with healthy weight range guidance; a calorie and TDEE calculator using the Mifflin-St Jeor formula; a body fat percentage calculator using the US Navy tape measure method; and a period and ovulation calculator for cycle tracking.
Why use SimplyCalc?
Calculator sites tend to be either very simple (one number in, one number out) or extremely complex with registration requirements. SimplyCalc sits in the middle: each tool pairs a working calculator with a genuine editorial explanation of what the numbers mean, how the calculation works, and what affects the result in the real world — so you leave understanding your answer, not just having a number.
About SimplyCalc calculators
SimplyCalc provides free online calculators for the most common personal finance, health, and everyday maths questions. All formulas are based on published standards: WHO BMI classifications, Mifflin-St Jeor for calorie estimates, standard amortisation for mortgage and loan calculations, and current HMRC and IRS tax rates.
Our tools are built for users in the UK, USA, and Europe — currency and tax options are available where relevant. Calculators are reviewed regularly to keep rates and formulas current. Found an error? Contact us and we'll fix it within 48 hours.
Looking for a calculator we don't yet have? Suggest a tool — we add new calculators based on what users ask for most.