Budgeting & Income
Percentage Calculator
The everyday percentage questions in one place. Pick a mode — a percent of a number, one number as a percent of another, or the percent change between two numbers — enter your values, and get the answer instantly.
Tested against worked examplesHow we verify
15% of 200: 30
15% of 200
30
- Percent (X)
- 15%
- Of (Y)
- 200
Compare scenariosTry three values of one input
| First value (X) | |||
|---|---|---|---|
| 14% of 200 | 28 | 30+2 | 34+6 |
| Percent (X) | 14% | 15%+1% | 17%+3% |
Every other input stays at the value you set above — currently 15 for first value (x). Differences are measured against the first column.
Saved scenariosSave this calculation
Saved in this browser only — no account, and nothing is sent to us. Clearing your browser data deletes them.
How this calculator works
Three formulas: X% of Y = (X ÷ 100) × Y; X is what percent of Y = (X ÷ Y) × 100; percent change from X to Y = ((Y − X) ÷ X) × 100. Division-by-zero cases (a zero whole or starting value) return 0 rather than an error.
A pure arithmetic tool — no money units or rounding assumptions. It handles negative numbers, so you can measure changes that cross zero.
What this assumes
- Pure arithmetic with no financial assumptions at all.
- Percentage change is measured against the starting value, which is why a rise and a fall of the same percentage do not cancel.
- It does not round intermediate steps, so results may differ slightly from mental arithmetic.
What changes this number
- Which value is the base
- The most common source of error. 'X is what percent of Y' and 'Y is what percent of X' are different questions.
- Direction of change
- A 50% fall requires a 100% rise to recover — the asymmetry that makes losses expensive.
- Compounding
- Successive percentage changes multiply rather than add.
A worked example
Take the 15% of 200 scenario. These figures are produced by the calculator above, not written alongside it, so they always match what the tool returns.
What you enter
- What do you want to find?
- What is X% of Y
- First value (X)
- 15
- Second value (Y)
- 200
What it returns
- 15% of 200
- 30
- Percent (X)
- 15%
- Of (Y)
- 200
Try an example
Frequently asked questions
How do I calculate a percentage of a number?
Multiply the number by the percentage divided by 100. To find 15% of 200: 200 × (15 ÷ 100) = 30. The 'What is X% of Y' mode above does this — useful for tips, discounts, commissions, and tax.
How do I find what percentage one number is of another?
Divide the part by the whole and multiply by 100. If you scored 25 out of 200, that's 25 ÷ 200 × 100 = 12.5%. Use the 'X is what percent of Y' mode for grades, savings rates, or progress toward a goal.
How do I calculate percent increase or decrease?
Subtract the old value from the new, divide by the old value, and multiply by 100. From 100 to 150 is (150 − 100) ÷ 100 × 100 = 50% increase; from 150 to 100 is a 33.3% decrease. Note that a 50% rise followed by a 50% fall does not return you to the start.
Why isn't a 50% gain cancelled by a 50% loss?
Because each percentage applies to a different base. $100 up 50% is $150; $150 down 50% is $75 — not $100. This asymmetry matters a lot in investing, where a 50% loss needs a 100% gain to recover.
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Disclaimer: DayCents provides this calculator for educational purposes only. Results are estimates based on your inputs and the stated assumptions — they are not financial advice, a quote, or an offer of credit. Consult a qualified financial professional before making major money decisions.