A walkthrough, end to end.
- 1
Pick a mode: X% of Y, X is what % of Y, or X is Y% of what.
- 2
Enter the two known values; the calculator returns the third.
- 3
Use the same tool for sales tax, tips, discounts, percent change and any other %.
Three forms
All percentage questions reduce to three forms. Knowing any two of (part, whole, percent) lets you solve for the third. Multiplication and division on a single line — no formula memorization needed.
What you can do with this.
Tip calculation
20% tip on a $42 bill: 0.20 × 42 = $8.40. Use mode 'X% of Y' with 20 and 42. Quick mental math also works: 10% = $4.20, double for 20%.
Sales tax
7.5% sales tax on $250 purchase: 0.075 × 250 = $18.75. Total = $268.75. The calculator returns just the tax amount — add to the original price.
Discount price
30% off a $80 jacket: $80 × 0.30 = $24 saved; final price $56. For the actual sale price, use the discount calculator (related).
Percent of total
Mode: 'X is what % of Y'. Sales of $45,000 against quota of $60,000 = 75%. Useful for goal tracking, dashboards, and progress reports.
Reverse percentage (find the original)
Mode: 'X is Y% of what'. If $80 is 25% off the original price, the original was $80 ÷ 0.75 = $106.67. Frequently needed for tax refund or net-of-fee calculations.
Percent change (increase / decrease)
Increase from 50 to 65: change = 15, % = 15/50 = 30%. The calculator's mode 'X is what % of Y' gives raw ratio; subtract 100 for percent change relative to the original.
Grading and test scores
27 correct out of 35 questions: 27/35 = 77.14%. Use the calculator's 'X is what % of Y' mode. Most schools round — 77% might map to grade C+.
Percentage calculator 2026 — what's current
Voice assistants and spreadsheet AI handle simple percents reliably. Stand-alone calculators still win on speed for one-off calculations and when you don't trust the autocomplete.
Frequently asked.
Percent is multiplicative; percentage points are additive. Going from 10% to 12% is a 2 percentage point increase OR a 20% relative increase. Mixing them up creates real confusion in finance and statistics.
((New − Old) / Old) × 100. Going from 50 to 65: ((65−50)/50) × 100 = 30% increase. Going from 65 to 50: ((50−65)/65) × 100 = −23% decrease. Direction matters — same difference, different %.
Increasing 100 by 20% gives 120. Decreasing 120 by 20% gives 96, NOT back to 100. Asymmetry between % and reverse % is a common math trap.
No. Calculations run entirely in your browser.