Enter two or more positive or negative numbers to calculate their exact sum, running totals, average, and value composition. You can also solve for a missing addend.
Sum Calculator
Enter numbers
The total that all known and missing addends must equal.
Advanced options
Your settings stay in this browser and are not sent anywhere.
Result
Enter at least two valid numbers to calculate.
Value composition
Bars are proportional and intended for visualization; use the displayed values for exact results.
Detailed breakdown
| Item | Operation or detail | Result |
|---|
Formula and Calculation
General formula
Substitution
Calculation
Exact result
Displayed result
How to Use This Tool
- Choose whether to calculate a sum or find a missing addend.
- Enter each number, including a minus sign for negative values.
- Add or remove number rows as needed.
- Select the desired display precision.
- Press Calculate and review the result, formula, and running totals.
- Copy, share, print, or download the calculation when needed.
How the Calculation Works
In standard sum mode, each entered value is combined in order. Positive values increase the running total, while negative values reduce it.
In missing-addend mode, the known values are summed and their subtotal is subtracted from the target total.
Formula Explanation
For a standard sum, S = a₁ + a₂ + … + aₙ, where each a is an addend and n is the number of values.
For a missing addend, x = T − (a₁ + a₂ + … + aₙ), where T is the required target total.
Worked Example
For 1,250.75, 349.20, −99.95, and 18, the sum is 1,518 because 1,250.75 + 349.20 − 99.95 + 18 = 1,518.
If the target total were 2,000, the missing addend would be 482.
Understanding the Results
The main result is the exact sum or missing addend, formatted using the selected precision. Supporting results show the number count, subtotal, average, or target.
The detailed schedule records how every number changes the running total.
Common Mistakes
- Leaving out a minus sign from a negative value.
- Using a comma as the decimal separator instead of a period.
- Entering incorrectly grouped thousands separators.
- Rounding individual values before calculating the final sum.
- Confusing the target total with a known addend.
Technical Notes
The calculator aligns decimal places and uses integer-based decimal arithmetic. This prevents common binary floating-point artifacts such as 0.1 + 0.2 displaying as 0.30000000000000004. Inputs may contain up to 15 integer digits and 12 decimal places. Rounding is applied only for display.
Frequently Asked Questions
Can I sum negative numbers?
Yes. Enter a minus sign before each negative value, such as −12.5.
Can I enter decimals?
Yes. Use a period as the decimal separator. Up to 12 decimal places are supported.
Why are trailing zeros displayed?
A fixed precision selection deliberately pads the result. Choose Auto to remove unnecessary trailing zeros.
How many numbers can I sum?
You can enter between 2 and 100 values in one calculation.
What is a missing addend?
It is the value that must be added to the known numbers to reach a specified target.
Are thousands separators allowed?
Yes. Correctly grouped commas are accepted, as in 12,500.75.
Are my values transmitted anywhere?
No. Calculations remain in your browser. Saved settings stay on this device.
Important Note
Check source values, signs, and required rounding rules before relying on a result for financial, scientific, engineering, or other consequential work. This calculator is a general arithmetic aid, not professional certification.