Free tools & calculators
20 calculators that run entirely in your browser — no sign-up, nothing stored. Each one comes with a plain-language explanation of the math, so you learn the idea, not just the answer.
Finance
Compound interest calculator
See how savings grow with compound interest. Enter a starting balance, regular contribution, rate, and time to project your future balance and total interest earned.
Free toolSavings goal calculator
Work out how much to set aside each month to reach a savings goal by a target date, including the interest your balance earns along the way.
Free toolLoan payment calculator
Work out the monthly payment on a loan from the amount, interest rate, and term — and see the total interest you’ll pay over its life.
Free toolSimple interest calculator
Calculate simple interest on a principal over time, and see how it differs from compound interest on the same amount.
Free toolTip calculator
Add a tip and split the bill in seconds — choose a percentage, see the tip and total, and divide it evenly between any number of people.
Free toolInflation calculator
See what a sum of money will be worth after inflation, and how much purchasing power it quietly loses over a number of years.
Free toolROI calculator
Calculate return on investment: enter what you put in and what it became to see the net gain, total ROI percentage, and an annualized rate for fair comparison.
Free toolDebt payoff calculator
See how long it takes to pay off a debt and how much interest it costs. Enter the balance, interest rate, and monthly payment to get your payoff time and total interest.
Free toolDiscount calculator
Work out a sale price and how much you save. Enter the original price and the discount percentage to get the final price and your total saving instantly.
Free toolNet worth calculator
Add up your assets and subtract your liabilities to find your net worth. A simple snapshot of financial health you can track over time — private and in your browser.
Free tool
Statistics
Percentage calculator
Three everyday percentage questions in one place: what is X% of Y, X is what percent of Y, and the percentage increase or decrease between two numbers.
Free toolMean, median & mode calculator
Paste a list of numbers to get the mean, median, mode, and range instantly — with a plain-language note on which average to trust for your data.
Free toolStandard deviation calculator
Calculate the standard deviation and variance of a data set — both population and sample — and see the mean and spread explained in plain language.
Free toolZ-score calculator
Convert a value into a z-score — how many standard deviations it sits from the mean — and read what that says about how unusual it is.
Free toolWeighted average calculator
Calculate a weighted average when some values count for more than others — enter each value with its weight and get the result instantly.
Free toolConfidence interval calculator
Build a confidence interval for a mean from the sample mean, standard deviation, and size — and see the margin of error in plain language.
Free toolSample size calculator
Find how many responses a survey needs. Choose a confidence level and margin of error (and optional population) to get the recommended sample size.
Free tool
Learning
Business
Profit margin calculator
Work out profit margin and markup from a selling price and cost. See the profit, the margin as a percentage of price, and the markup as a percentage of cost.
Free toolBreak-even calculator
Find how many units you must sell to cover your costs. Enter fixed costs, price per unit, and variable cost per unit to get the break-even point in units and revenue.
Free tool