Sum Calculator (Add Numbers)

How to use it

1. Type or paste the numbers you want to add.
2. The running total appears immediately.
3. Use the count and average below to double-check your list.

What is a sum?

A sum is the total, or aggregate, you get by adding numbers together. The math is the simplest in arithmetic:

sum = a1 + a2 + a3 + ... + an

The sample list, 12.50 + 8 + 19.99 + 4, totals 44.49. What makes a running total hard in practice is volume: a page of receipts or a long spreadsheet column invites slips, and one missed decimal point throws the whole answer. The calculator reads every number in the text you paste, adds them at full precision, and shows the count beside the total so you can confirm nothing was dropped or counted twice along the way.

Worked example

Mental addition shortcuts

Adding a long list of numbers

Adding numbers by hand invites slips, especially with decimals and long columns. Paste the whole list here and the total appears at once, with the count so you can confirm nothing was dropped. The sample list, 12.50 + 8 + 19.99 + 4, totals 44.49 across four items, for an average of 11.12. The tool reads any run of digits, so a column copied straight from a spreadsheet, a receipt or an email works without cleanup, and currency symbols and unit labels are simply skipped.

The average, minimum and maximum give quick context. If the average looks off, the min and max usually point to a stray value, like a price entered without its decimal point. A count that is one higher than expected often means a date or an order number got swept in along with the amounts.

What the number reader does and does not catch

The parser treats a comma as a separator, not a thousands mark, so 1,200 is read as 1 and 200 and adds up to 201. Strip the commas from large numbers first, or type them as 1200. A hyphen directly in front of a number is read as a minus sign, which is what you want for refunds and adjustments, but it also means a range like 10-20 becomes 10 and negative 20. Scientific notation such as 2.5e3 is understood as 2,500. Dates like 9/4/2026 are split into three separate numbers, so paste only the amount column when you copy from a table.

For a long run of consecutive whole numbers there is a shortcut: the sum of 1 through n is n × (n + 1) ÷ 2, so 1 through 100 adds up to 5,050. Any list you can actually type, though, is faster to paste. Results are shown to two decimal places, which is enough for money and most measurements, and the arithmetic itself is done at full precision.

Common uses

• Totaling receipts, invoices and expenses
• Adding a column pasted from a spreadsheet
• Checking a hand-added total
• Summing scores, hours or quantities
• Reconciling a bank statement line by line
• Adding up mileage or time entries for a claim

When to use it

• You need to add up a list of numbers from receipts before filing an expense report.
• You want to add a column of numbers pasted from Excel without writing a formula.
• You are totaling work hours or mileage entries for an invoice.
• A hand-added total looks off and you want a fast second opinion with a count check.

Related tools

The Average Calculator reads the same lists but leads with the mean, median and mode.

The Percentage Calculator takes your total the rest of the way, adding tax or splitting a share.

The Rounding Calculator trims a messy total to clean dollars or thousands.