Free Online Calculators — Instant Results in Your Browser
Calculate age, percentages, date differences, and more. All calculations run locally in your browser — your inputs are never sent anywhere.
Get Started →All Tools
Age Calculator
Calculate current age from a birth date.
Percentage Calculator
Compute percentage and remaining values from part and total.
Ratio Calculator
Simplify and analyze two-part ratios.
Date Difference Calculator
Calculate days, weeks, and months between two dates.
Random Number Generator
Generate random integers in a custom range.
Timestamp Converter
Convert Unix timestamps and date strings instantly.
Length Unit Converter
Convert values between common length units.
Enter your values and see results immediately. No submit button, no page reload, no waiting.
All calculations happen in your browser. Your inputs are never sent to a server or stored anywhere.
Every calculator is free with no usage limits, no account required, and no hidden fees.
No registration needed. Open any calculator and start working immediately.
Frequently Asked Questions
How accurate are the calculations?
All calculations use JavaScript's IEEE 754 double-precision arithmetic, which provides 15–17 significant digits of accuracy — sufficient for everyday calculations, finance, and most engineering use cases.
Are my inputs sent to a server?
No. Every calculation runs entirely in your browser. Nothing you enter is transmitted over the network.
How does the age calculator work?
Enter your birth date and the Age Calculator computes your exact age in years, months, and days as of today — or as of any target date you specify.
What can the percentage calculator do?
The Percentage Calculator can find what percentage one number is of another, calculate a percentage of a number, and find percentage increase or decrease between two values.
How do I calculate the number of days between two dates?
Open the Date Difference calculator, pick a start date and an end date, and the tool shows the exact number of days, weeks, months, and years between them.
Can I use these calculators offline?
Yes. Once the page has loaded, all calculators work without an internet connection because all processing happens in your browser.
How to calculate age from a birth date
Open the Age Calculator and enter a birth date. The tool instantly displays the current age in years, months, and days. You can also enter a target date to calculate age at any point in time — useful for historical research or planning.
How to calculate a percentage
Open the Percentage Calculator and choose the calculation type: percentage of a number (e.g. 15% of 200), what percentage one number is of another, or the percentage change between two values. Enter the values and the result appears immediately.
How to find the number of days between two dates
Open the Date Difference tool, select a start date and an end date, and the calculator shows the exact duration in days, weeks, months, and years. It accounts for leap years automatically.