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Percentage Calculator

Percentages show a value “out of 100,” which makes comparisons quick—whether you’re checking a discount, measuring growth, or converting a score into a grade. Use this Percentage Calculator to solve the most common percent questions in seconds, then copy a clean summary for notes or sharing. If you’re working with everyday pricing, you may also find the discount calculator useful.

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Calculate the exact percentage you need

Tip: results default to 2 decimals. Enable “More precision” to show up to 6 decimals.

Instant • Local • Private

Find the part when you know the percent and the whole.

You can type commas or decimals.
This is the base value the percent is applied to.

Convert one value into a percent of another value.

This is the part.
This is the whole (cannot be 0).

Measure how much something changed relative to the original value.

This is the starting (base) value.
This is the updated value after the change.

Apply a percent increase or decrease to a number and get the final value.

This is the base value.
This percent will be added or subtracted.
Choose whether to add or subtract the percent.

Work backward: if you know the final value after a percent change, find the original.

This is the value after the change.
The percent increase/decrease applied to the original.
Example: “After decrease” means the final is smaller than the original.
Rounding policy: show 2 decimals by default to keep results readable. Enable more precision to show up to 6 decimals.

How it works (formulas + step-by-step)

This Percentage Calculator covers the most common real-world percent tasks: “part of a number,” “percent of a total,” percent increase/decrease, applying a percent adjustment, and working backward with reverse percentages. These show up in shopping (discounts and markups), grades, analytics conversion rates, taxes and tips, and basic finance. If you’re comparing outcomes in class or at work, the grade calculator can pair nicely with percent calculations.

For finance-style percent growth, you might also check the compound interest tool when “percent per period” repeats over time.

Mode A (What is P% of N?)
Formula: Result = (P / 100) × N
Complement: (100 − P)% of N = ((100 − P) / 100) × N

Mode B (X is what percent of Y?)
Formula: Percent = (X / Y) × 100

Mode C (Percent change: Old → New)
Formula: % Change = ((New − Old) / Old) × 100
Absolute change: Δ = New − Old

Mode D (Add/Subtract P% to/from N)
Add: Final = N × (1 + P/100)
Subtract: Final = N × (1 − P/100)
Delta amount: N × (P/100)

Mode E (Reverse percentage)
After increase: Original = F / (1 + P/100)
After decrease: Original = F / (1 − P/100) (P ≠ 100)
Step-by-step (from your last calculation)
Selected mode: —

Formula: Run a calculation to see the exact formula here.
Substitute: —
Compute: —

Note on rounding: the display uses 2 decimals by default for readability. Toggle “More precision” above to show up to 6 decimals when you need it.

A quick sanity-check trick: if 10% of 200 is 20, then 12.5% should be a bit more than 20 (it’s 25). Estimations like this help catch direction mistakes.

Common use cases

  • Discounts and markups: find the sale amount (e.g., 15% off), or compute the marked-up price.
  • Grades and scoring: convert correct answers into a percent score (and compare attempts).
  • Business & analytics: calculate conversion rate, CTR, or completion percentage from totals.
  • Growth rates: measure how revenue, followers, or inventory changed from last month to this month.
  • Taxes and tips: apply a percent add-on to a subtotal to estimate totals quickly.
  • Nutrition labels: interpret “% Daily Value” as part-of-100 comparisons.

Worked examples

Example 1: What is 12.5% of 200?

Inputs: P = 12.5, N = 200

Steps: Convert percent to decimal: 12.5% = 0.125. Multiply: 0.125 × 200.

Final result: 25

Example 2: Percent increase from 80 to 100

Inputs: Old = 80, New = 100

Steps: Difference = 100 − 80 = 20. Divide by old: 20 / 80 = 0.25. Convert to percent: 0.25 × 100.

Final result: 25% increase

Example 3: Reverse percentage (final is 120 after a 20% increase)

Inputs: F = 120, P = 20, direction = after increase

Steps: Convert to multiplier: 1 + 20/100 = 1.2. Work backward: Original = 120 / 1.2.

Final result: 100

Common mistakes to avoid

  • Mixing up the base: percent change uses the old value as the denominator, not the new value.
  • Percent vs percentage points: going from 40% to 50% is +10 percentage points, but +25% relative change.
  • Dividing the wrong direction: for “X is what percent of Y,” it’s X ÷ Y (not Y ÷ X).
  • Forgetting to convert: 15% is 0.15 as a decimal multiplier.
  • Rounding too early: rounding intermediate steps can noticeably change the final percent—use more precision when needed.
  • Assuming change from zero is normal: percent change from 0 is undefined; use absolute difference instead.

Quick tips

  • Use complements: if you know 18%, you also know 82% (100% − 18%).
  • Estimate first: 10% is easy; scale up/down to sanity-check results.
  • Keep units consistent: don’t mix dollars and cents, or different measurement units, in the same ratio.
  • Check the base for change: percent change is “change relative to where you started.”
  • Use decimals for repeated operations: multiplying by 1.075 repeatedly is cleaner than re-applying 7.5% each time.
  • Toggle precision when needed: 2 decimals is great for display; 6 decimals helps auditing and edge cases.

FAQ

Percent change measures how much a value moved relative to a starting point: ((New − Old) / Old) × 100. It’s directional (increase or decrease) and depends on which value you pick as the base. Percent difference compares two values without treating either as “the start,” often using the average as the denominator, which makes it symmetric. If you specifically need a symmetric comparison, use the Percentage Difference Calculator. For time-based growth (old → new), percent change is usually the right choice.
Percentage points describe the simple gap between two percentages. If a rate goes from 30% to 36%, that’s a +6 percentage point change. Percent (relative change) asks how big the change is compared to the starting rate: (36 − 30) / 30 = 0.2, which is a 20% increase. Both can be correct; they answer different questions. Use percentage points when talking about a direct difference in rates, and use percent change when you want a relative growth or decline.
Yes. Negative inputs can be meaningful in contexts like net profit (loss), temperature changes, or signed differences. For “X is what percent of Y,” a negative X or Y will produce a negative percent, which indicates direction relative to the base. For percent change (Old → New), a negative old value can flip the sign in ways that may look surprising, so it helps to interpret what the base represents in your situation. The calculator will still compute safely and display a readable explanation.
Most real-life percentage answers are easiest to read at two decimals, especially for money, grades, and summaries. That’s why this page shows 2 decimals by default. When you need audit-level detail (like comparing nearly-equal values or verifying a worksheet), enable the “More precision” toggle to show up to 6 decimals. The underlying computation is done using standard floating-point arithmetic in your browser, and the toggle controls display formatting rather than changing the input values you entered.
Reverse percentage means you know the final value after a percent change, and you want the original. Think in multipliers: a 20% increase means “multiply by 1.20,” so the original is Final ÷ 1.20. A 20% decrease means “multiply by 0.80,” so the original is Final ÷ 0.80. The key is using the correct multiplier (1 ± P/100). If the decrease is 100%, the multiplier becomes 0, which makes the original impossible to recover, so the calculator flags it clearly.
For a discount, use “What is X% of Y?” to find the amount off, then subtract it from the price. Example: 15% of 80 is 12, so the sale price is 68. For a markup, use “Add/Subtract X%” with the Add option. Example: add 25% to 40 → 40 × 1.25 = 50. If you only know the final price after a discount, use “Reverse %” with “after decrease” to estimate the original price before the discount was applied.
Some percent formulas require a denominator. If you try “X is what percent of Y?” with Y = 0, the percent is undefined because you can’t form a meaningful ratio to zero. For percent change, the denominator is the old value; if Old = 0 and New is not zero, the change would be infinite/undefined. In these cases, this calculator avoids showing NaN or Infinity and instead explains what’s undefined and provides a helpful alternative, like the absolute difference, so you still get a useful takeaway.
No. The Percentage Calculator runs entirely in your browser, so your inputs are processed locally on your device. This page does not need your data to compute results, and it is designed to work offline without external libraries. When you use the Copy buttons, the text is copied to your clipboard for your convenience, but the content is not transmitted by this calculator logic. If you refresh the page, the calculator starts fresh unless your browser itself auto-fills fields.

Trust, accuracy & methodology

Accuracy & Method: Calculations run locally in your browser using standard arithmetic. The display defaults to 2 decimals for readability, and you can enable up to 6 decimals for more precision.
Privacy-first: Inputs stay on your device. This tool does not require sending your numbers anywhere to compute results.
Rounding policy: 2 decimals by default; “More precision” reveals up to 6 decimals. Intermediate steps are shown clearly in the formula section.
Last Updated: —

Sources & References

  • Standard percent definitions and ratio interpretation (basic arithmetic textbooks).
  • Common business math formulas for percent change and percent-based adjustments.
  • Statistical interpretation of rates and proportions (introductory statistics references).
  • Practical rounding guidance for reporting numeric results (style and reporting conventions).

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