About FastCalc

FastCalc started with a simple frustration: look up an online calculator and you'll usually get a black box buried under ads that spits out a number without telling you what formula it used. We wanted one place that shows its work.

So that's the idea. All 100 calculators are free, there's nothing to sign up for, and every page gives you the formula, a worked example with real numbers, and the assumptions behind the answer.

What we cover

• Construction: Cubic Yards.
• Finance: 1031 Exchange Deadline, 15 vs 30 Year Mortgage, 401(k) and 65 more.
• Home Improvement: Faucet Leak Water Waste, Painting Time and Labor, Well Yield and Drawdown Test and 1 more.
• Lawn & Garden: Beaufort Wind Scale.
• Automotive: Auto Loan, How Much Car Can I Afford.
• Electrical: Electricity Cost.
• Math & Geometry: Decimal to Fraction, Earthquake Magnitude and Energy, Reading Fluency.
• Cooking & Food: As-Purchased vs Edible Portion, Baker's Percentage, Baking Pan Size Conversion and 12 more.
• Small Business: Budget Variance, Freelance Hourly Rate, Teen Work Hours Limit and 1 more.
• Time & Dates: Date Difference.

A quick word on estimates

A calculator can only work with the numbers and assumptions you give it. Our results are here to help you learn and plan, not to replace a licensed electrician, a structural engineer, a doctor or a tax pro. Always double-check important numbers before you spend money or cut into a wall. See our terms of use for the full details.

Spot a mistake?

We'd really like to hear about it. Send us a note and we'll take a look.