calctool.app

About calctool.app

calctool.app is a free collection of fast, browser-based calculators — built for anyone who needs a quick, reliable answer to an everyday math, money, or health question.

Every calculator runs entirely in your browser. No account required, no data sent to a server, no tracking beyond standard analytics. The goal is simple: useful calculators that load instantly and get out of your way.

Calculators

  • Loan Calculator — Calculate the monthly payment, total interest, and payoff total for any fixed-rate loan or mortgage.
  • Compound Interest Calculator — See how savings or investments grow over time with compound interest and optional regular contributions.
  • Sales Tax Calculator — Add sales tax to a price to find the tax amount and the total with tax.
  • BMI Calculator — Calculate your Body Mass Index from height and weight in imperial or metric units, with category ranges.
  • Calorie Calculator — Estimate your daily calorie needs (TDEE) from age, sex, weight, height, and activity level using the Mifflin–St Jeor formula.
  • Body Fat Calculator — Estimate body fat percentage from body measurements using the U.S. Navy method, in imperial or metric units.
  • Percentage Calculator — Find a percentage of a number, what percent one number is of another, and percentage increase or decrease.
  • Average Calculator — Calculate the mean, median, mode, range, sum, and count from any list of numbers instantly.
  • Fraction Calculator — Add, subtract, multiply, and divide two fractions — results are reduced to lowest terms automatically.
  • Tip Calculator — Calculate a tip and split the total across any number of people — see per-person and total amounts instantly.
  • Age Calculator — Find your exact age in years, months, and days from your date of birth, plus total days lived.
  • Date Difference Calculator — Count the number of days, weeks, and months between any two dates — perfect for deadlines and planning.

A note on accuracy

These calculators are provided for general information and estimation only. Health calculators are not medical advice, and financial calculators are not financial advice — for decisions that matter, consult a qualified professional.

Contact

Questions or feedback? Reach out on Bluesky.