What Is a Percentage Calculator?

A percentage calculator is an everyday tool for figuring out discounts, tips, tax amounts, grade scores, pay raises, and investment returns. This calculator covers eight common percentage problems so you get an instant answer without writing out formulas by hand.

How to Find a Percentage of a Number

Divide the percentage by 100 and multiply by the number. To find 18% of $250: (18 ÷ 100) × 250 = $45.

Everyday US examples:

20% tip on a $65 dinner bill: 20% of $65 = $13 tip → total $78.
7.5% sales tax on a $120 purchase: 7.5% of $120 = $9 → total $129.
15% off a $89.99 item: 15% of $89.99 = $13.50 → you pay $76.49.
6% 401(k) contribution on a $75,000 salary: 6% of $75,000 = $4,500 per year.

What Percentage Is X of Y?

Divide X by Y and multiply by 100. If you scored 43 out of 50 on a quiz: (43 ÷ 50) × 100 = 86%.

You've paid off $8,400 of a $22,000 car loan: 8,400 ÷ 22,000 × 100 = 38.2% paid.
Monthly rent of $1,850 on a $5,500 take-home income: 1,850 ÷ 5,500 × 100 = 33.6% — right at the standard housing affordability threshold.

Percentage Increase and Decrease

Formula: ((New − Old) ÷ |Old|) × 100. Use the % Increase or % Decrease tabs — no need to pick the direction first if you use % Change, which auto-detects it.

Pay raise example: Salary goes from $58,000 to $63,800. Increase = ((63,800 − 58,000) ÷ 58,000) × 100 = 10% raise.

Stock example: A share drops from $142 to $118. Decrease = ((142 − 118) ÷ 142) × 100 = 16.9% decline.

Inflation example: US CPI increased significantly between 2021 and 2023. If your grocery basket cost $200 in 2021 and now costs $246, that's a ((246 − 200) ÷ 200) × 100 = 23% cumulative rise.

Tip Calculator — Add a Percentage

The "Add a %" mode works as a tip and tax calculator. Enter the bill amount and the percentage you want to add. Common tip rates in the US: 15% (standard), 18% (good service), 20% (excellent service), 25% (exceptional).

Example: $94 dinner, 20% tip: $94 × 1.20 = $112.80 total. The tip alone is $18.80.

For sales tax: your state and local combined rate determines the %. California averages about 8.68%; Texas is 8.2%; New York City hits 8.875%. Enter your actual rate for an accurate total.

Remove a Percentage — Pre-Tax Price

If you know the total with tax included and want the pre-tax amount, divide by (1 + tax rate). Example: total $107.50 at 7.5% sales tax → $107.50 ÷ 1.075 = $100 pre-tax. The "Remove a %" mode does this automatically.

Percentage Difference

When comparing two values without a clear "before" and "after", use percentage difference. Formula: |A − B| ÷ ((|A| + |B|) ÷ 2) × 100. Two competing job offers: $72,000 vs $79,500. Difference = 7,500 ÷ 75,750 × 100 = 9.9% apart.

US-Specific Use Cases

GPA conversion: If you scored 91 out of 100 in each course: 91 ÷ 100 × 100 = 91% → roughly a 4.0 GPA range.
Down payment: 20% down on a $385,000 home = 20% of $385,000 = $77,000.
Federal income tax effective rate: If you owe $11,200 on $68,000 AGI: 11,200 ÷ 68,000 × 100 = 16.5% effective rate.
Credit card interest: 24.99% APR on a $3,500 balance — monthly interest ≈ 24.99% ÷ 12 × $3,500 = $72.89.
Business invoicing: Linked to Invoice24 for professional invoicing with automatic tax calculations.

Frequently Asked Questions

How do I calculate a 20% tip?

Multiply the bill by 0.20, or divide by 5. On a $55 bill: $55 ÷ 5 = $11 tip. Or use the "Add a %" tab, enter $55 and 20%, and get the total with tip in one step.

How do I calculate sales tax?

Multiply the pre-tax price by your tax rate ÷ 100. At 8%: $150 × 0.08 = $12 tax → $162 total. Use "Add a %" with your state/local rate.

What is the formula for percentage change?

((New − Old) ÷ Old) × 100. Positive result = increase; negative = decrease. The "% Change" tab auto-labels the direction for you.

How do I find the original price before a discount?

Divide the sale price by (1 − discount%). A $68 item after a 15% discount came from: $68 ÷ 0.85 = $80 original price. Use "Remove a %" with 15%.

What percentage is an A grade?

Most US grading scales: A = 90–100%, B = 80–89%, C = 70–79%, D = 60–69%, F below 60%. Use "What % is X of Y?" with your score and total possible points.

How do I calculate a pay raise percentage?

Enter your current salary in "From" and your new salary in "To" on the "% Increase" tab. Example: $52,000 → $56,160 = 8% raise.

Free to use, no account required. For invoicing and business finances, see Invoice24.