Best Free Calculator Tools Online

The Loan Calculator is one of the most practically useful financial tools available for free online. Enter the loan principal, annual interest rate, and term in months, and it returns the fixed monthly repayment amount plus the total interest paid over the life of the loan.

This is invaluable before signing any financing agreement. A car loan at 7% over 48 months looks very different in total cost from the same loan at 9% over 60 months — even if the monthly payments feel similar. The calculator makes that difference visible before you commit.

The Percentage Calculator handles the three most common percentage questions in one tool:

• What is X% of Y? (e.g. what is 15% of 340?)
• X is what percentage of Y? (e.g. 51 is what percentage of 340?)
• What is the percentage increase or decrease from X to Y?

These questions come up constantly in work settings — calculating a discount, figuring out a commission, checking a test score, or comparing monthly figures. Having a dedicated tool removes the risk of mental arithmetic errors under pressure.

The Age Calculator takes a date of birth and today's date and returns the exact age in years, months, and days. It also shows the next birthday and how many days until it arrives. This is used for filling in forms accurately, verifying age eligibility requirements, and the occasional curiosity about exact age in days.

The Date Difference Calculator does the same job for any two arbitrary dates — enter a project start date and deadline to see exactly how many working days are available, or check how long a warranty has been running.

The BMI Calculator computes Body Mass Index from height and weight in either metric or imperial units. The result is placed against the standard BMI categories: underweight (below 18.5), normal weight (18.5–24.9), overweight (25–29.9), and obese (30 and above).

BMI is a rough screening measure, not a complete health assessment. It does not account for muscle mass, bone density, age, or where body fat is distributed. Use the result as a starting point for a conversation with a healthcare professional rather than a definitive verdict.

Three everyday financial calculators cover common shopping and business scenarios:

• The VAT Calculator adds or removes VAT from a price at any rate. Enter the rate for your country — 20% in the UK, 7.5% in Nigeria, 15% in South Africa — and the tool handles both directions: price plus VAT, and VAT-inclusive price stripped back to the base.
• The Discount Calculator shows the sale price and the total saving for any original price and discount percentage.
• The Tip Calculator computes the tip amount and per-person total for any bill split between multiple diners.

Browse all available calculators on the Calculator Tools category page.