What changes the result most
Operation choice and the two entered values usually move the result most: 125 with 18 means 143 under addition but 22.5 when 18 is treated as a percent.
Basic Calculator
Calculate arithmetic, percentages, percent change, division, and powers with a clear operation label and keyboard-friendly inputs.
Runs locallyKeyboard friendlyUpdated: August 30, 2026
Enter your scenario
Results update as valid inputs change. Correct any highlighted field before relying on the answer.
Primary result
Result22.5
OperationPercent of value
First value125
Second value18
Absolute difference107
Percent of value produces 22.5 from the two entered values.
Use the result
From calculation to decision
Use this calculator when the operation matters as much as the answer. The result cards retain both entered values and name the selected arithmetic rule.
What to do next
Change one high-leverage input, compare the new result with the default, and confirm any current rate, policy, quote, or external rule that controls the real decision.
Save and report
Calculation happens in this browser. Shared links include the visible input values, so inspect the URL before sending a sensitive scenario.
If a result appears wrong, report an issue for this calculator.
When this calculation helps
Use this calculator when the operation matters as much as the answer. The result cards retain both entered values and name the selected arithmetic rule.
The result separates the primary answer from supporting values so you can see both the number and the assumptions that produced it. Adjust one field at a time when comparing scenarios; changing several inputs together makes it harder to identify why the answer moved.
Formula / methodology
Add: a + b
Subtract: a − b
Multiply: a × b
Divide: a ÷ b
Percent of: a × b ÷ 100
Percent change: (b − a) ÷ |a| × 100
Power: aᵇDivision rejects a zero divisor. Percent change rejects a zero starting value because its denominator would be zero. The parser also suppresses results outside JavaScript’s finite numeric range.
Assumptions and limitations
- Numbers are treated as decimal values, not currency or measurements.
- Percent change uses the absolute starting value as the denominator.
- The displayed result keeps up to ten decimal places; it is not symbolic exact arithmetic.
Worked examples
Find 18% of 125
Select “percent of.” The calculation is 125 × 18 ÷ 100 = 22.5.
Measure a price change
For a move from 80 to 92, select percent change: (92 − 80) ÷ 80 × 100 = 15%.
Common mistakes
- Entering 0.18 when the operation already treats the second value as a percentage.
- Reversing the start and end values in percent change.
- Expecting division by zero to produce a usable number.
FAQ
Does the calculator follow order of operations?
Each basic mode applies one named operation. Use the scientific calculator for a multi-operator expression.
Why is percent change unavailable from zero?
The normal formula divides by the starting value, so a zero start has no finite percentage change.
Sources and assumptions
The rules are standard arithmetic identities. See the CalculatorShelf Source Guide for how mathematical identities and example defaults are recorded.
Updated: August 30, 2026. Method: BASIC_ARITHMETIC-1.0. Inputs remain visitor-entered unless a data timestamp is shown beside them.
Calculator-specific review
Decision supported: Perform a clearly labeled arithmetic or percentage operation on two values.
Inputs and two scenarios
The inputs below are scenario controls, not facts supplied by a source. Change the values to see how this calculator responds to the decision you are making.
published default example: First value: 125; Second value: 18; Operation: First value × second value as a percent.
materially different higher basic calculator scenario: First value: 187.5; Second value: 27; Operation: Percent change from first to second.
What changes the result
The selected operation determines how each value affects the result; zero has special meaning for division and percent change.
Method and evidence boundary
The selected operation applies addition, subtraction, multiplication, division, percent, percent change, or exponentiation. The result follows the displayed arithmetic identity and uses no external data.