About CalculatorXP
Free, fast and accurate calculators for everyday life — finance, health, maths, science and dates. No sign-up required.
Categories
Finance
22 calculators — mortgage, loans, tax, investments, salary and more.
Health
11 calculators — BMI, BMR, calories, body fat, pace, heart rate and more.
Math
9 calculators — percentages, fractions, statistics, prime factors and more.
Science
8 calculators — unit converter, density, Ohm's law, periodic table and more.
What Is CalculatorXP?
CalculatorXP is a free collection of online calculators designed to be genuinely useful. Every calculator shows step-by-step working so you understand the result, not just the number. All calculators work on any device — mobile, tablet or desktop — and require no sign-up or download.
Our calculators are built with accuracy and clarity in mind. Where there are multiple established methods or formulas, we show them all. Results include context — visual bars, comparison tables and real-world examples — to help you make sense of the numbers.
Who's Behind CalculatorXP?
CalculatorXP is built and maintained by one person: I design the tools, write the code, and verify every formula myself. I started the site because most calculator sites bury a simple answer under ads and never show you how the result was reached. Every tool here shows its working. I keep my full name offline as a matter of personal privacy, but I stand behind every number on this site — and if you find an error, tell me and I'll fix it and credit you.
How Formulas Are Verified
Every calculator on this site is checked against published, primary sources before launch — not against other calculator websites. Specifically:
- Health tools use peer-reviewed equations cited by name on each page (e.g. Mifflin-St Jeor for BMR, WHO thresholds for BMI), with their known error margins stated rather than hidden.
- Finance tools use the standard amortization and compound-growth mathematics used by lenders, with worked examples on the page that you can re-verify by hand.
- Math and science tools are tested against known exact values and edge cases (leap years, exact conversion factors like 1 in = 2.54 cm, rounding behaviour).
When a calculator relies on data that changes over time — tax rates, for example — the tax year in force is stated on the page. If something looks out of date, it probably needs my attention: report it.
Our Categories
Accuracy and Limitations
CalculatorXP calculators use established formulas and are designed for general guidance. Health calculators use population-average formulas which may not perfectly reflect your individual situation. Financial calculators assume fixed rates and do not account for fees, penalties or tax unless stated. Always consult a qualified professional for important financial, medical or legal decisions.
Contact
Have a suggestion for a new calculator, spotted an error, or want to get in touch? We'd love to hear from you. Use the contact form or email us directly at hello@calculatorxp.com.