Free calculators that show their work

Seven fast tools for money, school, fitness, and baseball. Every one comes with the formula, worked examples, and sources, so you can trust the number you get.

Finance

Financial Freedom Calculator

See how long it takes to hit your savings target from monthly income and expenses.

Tip Calculator

Work out the tip, the total, and each person's share in a couple of seconds.

Mortgage Calculator

Estimate monthly payments, total interest, and payoff date.

Federal Income Tax Calculator

Estimate federal income tax by filing status with bracket breakdown.

Health

Max Heart Rate Calculator

Find estimated max heart rate with five formulas plus training zones.

Education

Cumulative GPA Calculator

Add courses with credits and grades to get your cumulative GPA.

Sports

ERA Calculator

Calculate earned run average for baseball and softball.

Why this site exists

It started with too many browser tabs open at once: a tip calculator here, a mortgage estimator there, a GPA tool buried under ads, and a tax calculator that only made sense in one country. The math was simple. Everything around it was not.

We built eCalculator as one calm home for the tools people reach for again and again. No clutter, no paywalls, no guessing about currency or filing status. Each page shows the formula, walks through real examples, and links to the sources we used. We test the numbers by hand before we ship.

Whether you are splitting a dinner bill, estimating a mortgage, checking a GPA, or figuring out training zones, you should get an answer you can explain to someone else. That is the whole point.