Free online calculators
Health, finance and math calculators that give you a result as you type — no signup, no downloads, nothing sent to a server.
Tools in this category8
- Scientific CalculatorTrigonometric functions, logarithms and exponentials
- BMI CalculatorBody mass index with classification table
- Age CalculatorCalculate your exact age in years, months and days
- Pregnancy CalculatorDue date and gestational age calculator
- Financial CalculatorInstallments, simple interest and financing
- Compound InterestSimulate investment growth over time
- Tip CalculatorCalculate the tip and split the bill between people
- Fuel Cost CalculatorCalculate the fuel cost of a trip
About these tools
Every calculator here runs entirely in your browser. You type the numbers, JavaScript does the arithmetic on your device, and nothing is uploaded — which is why they work offline once the page has loaded and why there is no account to create.
The health calculators (BMI, age, pregnancy) follow the standard reference tables used by health services, and the financial ones (compound interest, loan payments, tips, fuel cost) use the same formulas a bank or spreadsheet would. Each page shows the formula it applies so you can check the result yourself.
Frequently asked questions
Are these calculators free?
Yes. Every calculator on Smartntools is free and needs no account, no email and no installation.
Is my data sent anywhere?
No. The calculations happen in your browser. The numbers you type never leave your device.
Can I use them on my phone?
Yes. All calculators are built mobile-first and work in any modern browser on phone, tablet or desktop.