Ratio Percentage Calculator

Calculator

Calculation Type

Pick the problem style first.

Rounding (decimals)

Used for on-screen display.

Label (optional)

Adds context in your own notes.

Part

The portion or numerator value.

Whole

The total or denominator value.

Percentage (%)

Enter the percent value, not a fraction.

A

First ratio term.

B

Second ratio term.

Value 1

The new or compared value.

Value 2

The reference or baseline value.

Reset

Example data

Scenario	Input	Output
Part ÷ Whole → Percentage	25 / 200	12.5%
Ratio A:B → Percent Split	3 : 2	60% / 40%
Percent of Whole → Part	12.5% of 200	25
Part & Percent → Whole	25 at 12.5%	200
Compare Two Values	80 vs 64	1.25, 125%, +25%

Formula used

Percentage = (Part ÷ Whole) × 100
Part = (Percentage ÷ 100) × Whole
Whole = Part ÷ (Percentage ÷ 100)
A% = A ÷ (A + B) × 100, B% = B ÷ (A + B) × 100
Relative change (%) = (Value1 − Value2) ÷ Value2 × 100

Ratios are simplified using the greatest common divisor when inputs are integers.

How to use this calculator

Select a calculation type that matches your problem.
Enter the required numbers. Use decimals if needed.
Choose rounding for the on-screen output.
Press Submit to show results above the form.
Use Download CSV or Download PDF for reporting.

FAQs

1) What is a ratio?

A ratio compares two quantities using division, often written as A:B. It tells how many parts of one quantity exist for each part of another.

2) How do I convert a ratio to a percentage split?

Add the ratio terms to get the total parts. Divide each term by the total, then multiply by 100. The calculator does this and shows both shares.

3) Why must the whole be non‑zero?

Division by zero is undefined. If the whole or reference value is zero, a percentage and ratio value cannot be computed reliably.

4) Can I use decimals or large numbers?

Yes. The inputs accept decimals and large values. When simplifying ratios from decimals, the calculator scales up to six decimal places to reduce the ratio.

5) What does “relative change” mean?

Relative change compares Value1 against Value2 as a baseline. A positive result means Value1 is higher; a negative result means it is lower.

6) How is the ratio simplified?

For integer inputs, it divides both sides by the greatest common divisor. For decimal inputs, it scales to an integer form first, then simplifies.

7) Which rounding should I choose?

Use fewer decimals for clean reporting and more decimals for precision. Rounding affects display only; internal calculations use full precision.

8) What do the CSV and PDF downloads include?

They include the calculation label, key result values, and any notes. This helps you paste results into spreadsheets or share a quick report.