Clear answers for everyday money, health and school questions.
Practical calculators for loans, savings, salaries, BMI, grades, tips and more. They run in your browser, keep your numbers to yourself, and work on any device.
Finance calculators
16 toolsCompound Interest Calculator
See how interest builds on interest over time, and what a small head start is worth.
Salary to Hourly Calculator
Turn an annual salary into an hourly rate, or work out an offer in either direction.
Annual Income Calculator
Add up wages and hourly pay into a yearly figure, taking working hours into account.
Mortgage Payment Calculator
Estimate monthly payments on a home loan, including principal and interest.
Loan Payment Calculator
Work out regular payments and total cost for any fixed-rate loan.
ROI Calculator
Measure the return on an investment in percent, and see the gain in dollars.
Savings Goal Calculator
Find out what you need to set aside each month to hit a savings target.
Debt Payoff Calculator
See how much faster a bigger monthly payment retires a balance.
Net Worth Calculator
Add up what you own and what you owe to see your net worth.
Paycheck Calculator
See your take-home pay after federal tax, FICA and state tax, per pay period.
Income Tax Calculator
Estimate federal income tax, payroll taxes and your net income for the year.
Inflation Calculator
See what money will be worth later, and how much prices rise over time.
Car Payment Calculator
Work out your monthly auto loan payment from price, down payment and rate.
Retirement Calculator
Estimate how much your savings will grow, and what it buys as monthly income.
Amortization Calculator
See the monthly payment and full schedule of principal and interest on a loan.
Mortgage Affordability Calculator
Find out how much home you can afford based on income, debts and rates.
Everyday calculators
9 toolsTip Calculator
Split a bill and figure the tip, per person, without the maths.
Percentage Calculator
Work out percentage changes and parts of a number in three quick modes.
Discount Calculator
See the sale price after a percent off, and exactly how much you save.
Sales Tax Calculator
Add tax to a price or pull the tax out of a total you have already paid.
Age Calculator
Work out an exact age in years, months and days from any birth date.
Unit Converter
Convert length, weight, temperature and data storage between common units.
Hours Calculator
Figure out time worked between a start and end time, breaks included.
Fuel Cost Calculator
Estimate how much a trip costs in fuel, and what it adds up to each month.
Days Between Dates Calculator
Count the days, weeks and business days between any two dates.
How Countwell works
Every calculator on this site follows the same simple rules. The maths runs entirely in your browser, so nothing you type is sent anywhere or stored. There is no account to create and nothing to download.
Each page gives you the calculator up front, then a plain-English explanation of how the numbers are worked out, the formula behind it, and a worked example you can check by hand. A short disclaimer reminds you where an estimate ends and professional advice begins.
If a tool would be useful to you, it is probably useful to someone else too. That is the whole idea behind the site: small, honest calculators that save you a minute of mental arithmetic.