Percentage Calculator
Solve any percentage problem — change, increase, decrease, discount, tip, and what-percent-of-what.
Interactive Percentage Calculator
Result
Use this free percentage calculator to solve any of the four standard percentage problems — find a percentage of a number, find what percentage one number is of another, find a total from a part, or measure percentage change between two values.
How to use this percentage calculator
Select the calculation mode that matches your problem, then enter the values. The result appears instantly with the formula used. Five modes cover virtually every percentage scenario you encounter.
Quick reference for which mode to use:
- What is X% of Y? → Use when you know the percentage and want to find the part (e.g., 20% of 150)
- X is what % of Y? → Use when you know the part and want to find the percentage (e.g., 30 is what percent of 150)
- X is Y% of what? → Use when you know the part and percentage and want the whole (e.g., 30 is 20% of what)
- % change from X to Y → Use for growth, decline, or comparison over time
- X% off original price → Use for shopping discounts and sale prices
Worked examples
20% tip on a $48 bill: Mode = “What is X% of Y”, enter 20 and 48. Result: $9.60. Add to $48 for a total of $57.60.
A stock went from $120 to $150: Mode = “% change from X to Y”, enter 120 and 150. Result: 25% growth. The investment grew by one-quarter.
A $80 item is 25% off: Mode = “X% off original price”, enter 25 and 80. Result: discount $20, final price $60.
$30 is what percent of $150? Mode = “X is what % of Y”, enter 30 and 150. Result: 20%.
The sequential discount trap
“50% off, plus an additional 20% off” sounds like 70% off but is actually 60% off. The second percentage applies to the already-discounted price, not the original.
A $100 item at 50% off becomes $50. The additional 20% off that is $10, leaving $40. Total discount: $60, which is 60% of the original $100. Sequential discounts multiply: 0.5 × 0.8 = 0.4 of original, meaning 60% off.
The calculator handles this naturally when you run the second discount on the post-first-discount price.
Percentage change vs. percentage difference
Percentage change measures growth or decline relative to an original value: (new − old) / old × 100. A stock going from $100 to $120 is a 20% increase.
Percentage difference compares two values without designating an ‘original’: |a − b| / ((a + b)/2) × 100. Comparing $120 and $100 with this formula yields about 18.18%.
Use change when tracking performance over time. Use difference when comparing two unrelated numbers. Conflating the two is a common source of statistical error.
Tips for accurate percentage work
- Always identify the base. “Increased by 50%” means different things if the base is $10 or $10,000. Specify what the percentage is of.
- Round at the end. Intermediate rounding compounds error. Keep full precision until the final answer.
- Pair percentages with absolute numbers. “Saved 60%” sounds great but $3 saved on a $5 item is small. Show the dollar amount alongside the percentage.
- Be careful with sequential operations. Tax on a discounted price, compounded interest, and stacked percentages all multiply, not add.
Common pitfalls
- Comparing percentages of different bases. “Sales up 30% this year” tells you nothing without last year’s base. Use the dollar amount to put percentages in context.
- Confusing markup and margin. A 50% markup is a 33% margin. Always clarify which you mean when discussing pricing.
- Forgetting negative percentages. A change from 100 to 75 is a −25% change, not a 25% change. The sign matters.
Related Tools
- Discount Calculator – Calculate sale prices, stacked discounts, and savings.
- Tip Calculator – Calculate tips and split bills at restaurants.
- ROI Calculator – Measure return on investment for purchases or projects.
- Inflation Calculator – Convert historical dollars to today’s purchasing power.
- Mortgage Calculator – Calculate mortgage payments including taxes and insurance.
| Problem | Formula | Example | Result |
|---|---|---|---|
| 20% off $80 | $80 × (1 − 0.20) | Original $80, discount 20% | Final: $64 (savings $16) |
| 15% tip on $48 | $48 × 0.15 | Bill $48, tip 15% | Tip: $7.20, total $55.20 |
| $120 grew to $150 | ($150 − $120) / $120 | Start $120, end $150 | Gain: 25% (multiple 1.25x) |
| 30 is what % of 150 | 30 / 150 × 100 | Part 30, whole 150 | 20% |
| 20% markup on $50 cost | $50 × 1.20 | Cost $50, markup 20% | Price: $60 (margin 16.67%) |
Compare your options
Two methods, three minutes. The honest trade-off table.
This percentage calculator
- + Five modes covering all standard percentage problems.
- + Bidirectional: solve for unknown in any direction.
- + Plain-English explanations of the formula used.
- − Does not handle weighted averages or compound percentages.
Calculator.net / Omni
- + Wide variety of specialized percentage calculators.
- + Often includes printable reference charts.
- − Ad-heavy with multiple calculators per page.
- − Less intuitive for non-standard percentage problems.
Phone calculator app
- + Always available, no internet needed.
- + Fast for simple calculations.
- − No formula explanation — easy to misapply.
- − Switching between modes requires memorization.
Who actually uses Percentage Calculator?
Five concrete situations pulled from real sessions, with the exact inputs people paste in.
Know the actual discount and the final price before checkout.
Enter the original price and the discount percentage. The calculator shows the dollar amount off and the final price — useful when stores advertise 'up to 50% off' and you need the figure for your specific items.
A quick way to calculate the tip and per-person share.
Enter the pre-tip amount, the tip percentage, and the number of diners. The tool returns the tip, the total, and the per-person share — all in one screen.
Calculate percentage gain or loss over time.
Enter the original investment and the current value. The calculator returns the percentage change and the multiple, useful for comparing two assets with different starting prices.
Verify percentage problems and reverse-engineer unknowns.
Use the 'X is what percent of Y' mode to check your work, or 'X is Y% of what' to find a total when you know a part. The tool handles all four standard percentage problems.
Apply consistent markup to cost or back out margin from a price.
Enter your cost and target markup percentage. The tool returns the selling price. Switch to margin mode and enter the selling price to back out the margin.
A percentage calculator that solves any of the four standard problems — in any direction
Percentages show up in tipping, shopping, investing, taxes, and statistics — and the same problem can be set up four different ways. This tool handles all of them in one screen, with the formula explained in plain English. Whether you need to find the percentage, the part, or the whole, the answer is one or two clicks away.
All four standard percentage problems
What is X% of Y, X is what percent of Y, X is Y% of what, and percentage change between two values — plus reverse percentages and sequential discounts. The five modes cover virtually any percentage problem you encounter.
Formula shown, not just result
Each calculation displays the formula used and the intermediate steps. Useful for students checking work and adults verifying they applied the right operation.
Instant results, no submit button
Type any input and the answer updates in real time. For quick mental checks, that responsiveness matters more than elaborate output formatting.
Browser-only, no storage
Numbers you enter are processed locally and not transmitted. Use it for sensitive calculations without concern.
What you only get here: a percentage calculator with all four problem types in one place, plain-English formula explanations, and instant results — without ads or signup.