Free online calculators for finance, health, math and more

CalcSkit — find the answer, understand it. Fast, free calculators with instant results and clear explanations: every tool shows the formula it uses, a worked example and answers to common questions. No account, no download.

Popular calculators

Mortgage Calculator — monthly payment, total interest and a yearly amortization schedule for any home loan.
Loan Calculator — loan repayment calculator for car, personal and student loans.
Compound Interest Calculator — savings calculator showing how deposits and monthly contributions grow.
BMI Calculator — BMI calculator online with WHO category and healthy weight range, metric or imperial.
Calorie Calculator — BMR and daily calorie needs (TDEE) via the Mifflin-St Jeor equation.
Percentage Calculator — X% of Y, X as a percent of Y, and percentage change, with steps shown.

Browse calculators by category

Finance calculators — loans, mortgages, savings and interest.
Health & fitness calculators — body metrics and nutrition.
Math calculators — percentages and everyday math.
Other calculators — dates, conversions, tips and practical tools.
Explore all online calculators — the complete index.

Why use CalcSkit?

Every calculator is 100% free and works without registration. Results update instantly as you type and come with a plain-language explanation, the exact published formula (standard amortization for mortgages and loans, WHO ranges for BMI, Mifflin-St Jeor for calories), a worked example and a short FAQ. Each tool also generates shareable links that reopen it with your exact values.

Frequently asked questions

Are CalcSkit calculators really free?: Yes. Every calculator on CalcSkit is completely free to use, with no account, no sign-up and nothing to download.
Do I need an account to save or share a calculation?: No. Every tool works anonymously, and the Share button on each calculator creates a link that reopens it with your exact values already filled in.
How accurate are the results?: Each calculator uses standard, published formulas — the same fixed-rate amortization formula lenders use, WHO ranges for BMI, and the Mifflin-St Jeor equation for daily calories. The exact formula and a worked example are shown on every page.
Which calculators are the most popular?: The mortgage calculator, the BMI calculator and the percentage calculator are the most used tools, followed by the loan repayment calculator and the compound interest calculator.
Do the calculators work on mobile?: Yes. Every page is designed mobile-first, works in any modern browser, and supports both light and dark mode.
How often are new calculators added?: The catalog grows regularly. Recent additions include a calorie (TDEE) calculator, a tip calculator, an age calculator and a length converter. A salary calculator and a tax calculator are next on the roadmap.