Addition Calculator

Addition combines two or more amounts into one total. If you have 7 stickers and get 5 more, 7 + 5 = 12. The numbers you add are called addends and the total is called the sum. This addition calculator adds as many numbers as you like, including decimals and negative numbers, and it shows the carrying step by step.

• Addend: a number that is being added. In 7 + 5 = 12, the addends are 7 and 5.
• Sum (or total): the result of the addition (12).
• Plus sign (+): the symbol for addition.

Write the numbers under each other so the units, tens and hundreds line up, and add one column at a time starting from the right. If a column adds up to 10 or more, write the units digit and carry the tens digit to the next column. Here is 478 + 256.

1. Units: 8 + 6 = 14. Write 4 and carry 1 to the tens column.
2. Tens: 7 + 5 + 1 (carried) = 13. Write 3 and carry 1 to the hundreds column.
3. Hundreds: 4 + 2 + 1 (carried) = 7. Write 7.
4. Read the answer: 478 + 256 = 734.
5. Check by estimating: 480 + 260 = 740, which is close to 734.

The step-by-step player under the result shows the same working for your numbers, with the carries in orange above the next column. It works for three, four or more numbers as well.

Line up the decimal points, add zeros so every number has the same number of decimal places, and add column by column. 3.75 + 2.5 becomes 3.75 + 2.50 = 6.25. Computers that use floating point often show 0.1 + 0.2 as 0.30000000000000004; this calculator is exact and gives 0.3.

• Same signs: add the sizes and keep the sign. (−4) + (−6) = −10.
• Different signs: subtract the smaller size from the larger and keep the sign of the larger. (−5) + 3 = −2, and 7 + (−10) = −3.
• Adding a negative number is the same as subtracting: 7 + (−3) = 7 − 3 = 4.

• Commutative property: the order does not matter. 9 + 4 = 4 + 9 = 13.
• Associative property: grouping does not matter. (2 + 3) + 5 = 2 + (3 + 5) = 10. This lets you add in any order.
• Identity property: adding zero changes nothing. 58 + 0 = 58.
• Inverse property: a number plus its opposite is zero. 8 + (−8) = 0.

• 47 + 38 = 85 (7 + 8 = 15, carry 1; 4 + 3 + 1 = 8).
• 12 + 18 + 25 + 40 = 95 (12 + 18 = 30, 25 + 40 = 65, 30 + 65 = 95).
• 3.75 + 2.5 = 6.25.
• 0.1 + 0.2 = 0.3.
• 999 + 1 = 1,000 (the carry travels through every column).
• (−12) + 20 = 8.

• Make a ten: 8 + 7 = 8 + 2 + 5 = 10 + 5 = 15.
• Round and adjust: 68 + 29 = 68 + 30 − 1 = 97.
• Add the big parts first: 346 + 125 = 300 + 100, 40 + 20, 6 + 5 = 400 + 60 + 11 = 471.
• Look for pairs that make 10, 100 or 1,000 when adding a list.

You add to total a shopping bill, combine expenses in a budget, find the perimeter of a shape, count scores, add hours worked across a week, or combine ingredient amounts. Any time you ask "how many altogether" or "what is the total", you add.