Money Math Calculator
Add, subtract, multiply, split, and stretch money to the cent. Column layouts for dollars-and-cents, even splits rounded down, and how many items a budget buys.
Doing math with money
Money is just decimals with two places — dollars and cents. The trick is keeping the decimal points lined up and padding whole dollars with .00.
Adding and subtracting
Stack the amounts so cents sit under cents, pad to two places, and add or subtract in columns.
$45.70 + $191.00 + $20.65 = $257.35, and $141.75 − $35.50 = $106.25.
Multiplying by a count
Buying several of the same item is multiplication. Multiply as whole numbers, then place the decimal two from the right: $52.60 × 12 = $631.20.
Splitting a bill
Divide the total by the number of people. $34.80 ÷ 3 = $11.60 each. When it does not split evenly to the cent, the share is rounded down to the nearest cent.
How many can I buy?
Divide the budget by the price, counting only whole items. Convert to whole cents first: $560.00 → 56000 and $9.20 → 920, then 56000 ÷ 920 = 60 items with $8.00 left over.
Common mistakes
- Not padding whole dollars to .00 before lining up columns.
- Misplacing the decimal point when multiplying.
- Rounding a split up instead of down to the cent.
For adding a percentage on top, see sales tax and tip; the column methods come from long addition and its siblings.
Frequently asked questions
- How do you add money amounts?
- Line up the decimal points so cents sit under cents, pad whole dollars with .00, then add in columns from the right. So $45.70 plus $191.00 plus $20.65 is $257.35.
- Why write $191 as $191.00?
- Money always uses two decimal places for cents. Padding a whole dollar amount to $191.00 keeps the decimal points aligned so the columns add correctly.
- How do you multiply money by a quantity?
- Treat it like decimal multiplication — multiply as whole numbers and place the decimal two from the right. So $52.60 times 12 is $631.20.
- How do you split a bill evenly?
- Divide the total by the number of people. $34.80 split among 3 is $11.60 each. If it does not divide evenly to the cent, the result is rounded down to the nearest cent.
- How do you work out how many items a budget buys?
- Divide the budget by the price, but only whole items count. Working in whole cents, $560.00 divided by $9.20 is 60 items with $8.00 left over.
- Why convert dollars to cents for that division?
- Turning $560.00 into 56000 cents and $9.20 into 920 cents makes it a whole-number division, which cleanly gives a whole number of items and a whole-cent remainder.
- Can a money amount have three decimal places?
- Not for cash. Prices are quoted to the cent, so this calculator accepts at most two decimal places. Fractional-cent prices (like fuel) are a separate case.