Percentage Calculator: How to Calculate Discounts, Sales Tax, and Tips in Seconds

Percentages are everywhere in daily life — shopping discounts, sales tax, restaurant tips, commission rates, interest rates, and grade calculations. Knowing how to calculate percentages quickly and accurately saves you money, helps you budget better, and prevents embarrassing math mistakes at the checkout counter.

Use our free Percentage Calculator at Today Calculator for instant percentage calculations — no formulas to memorize.

Three Core Percentage Formulas

You Want To	Formula	Example
Find what % of X is Y	(Y ÷ X) × 100	What % of 200 is 50? → (50÷200)×100 = 25%
Find X% of Y	(X ÷ 100) × Y	15% of 80 → (15÷100)×80 = 12
Increase/decrease Y by X%	Y × (1 ± X÷100)	50 increased by 20% → 50×1.2 = 60

Real-World Percentage Scenarios

Shopping Discounts

A “30% off” sale on a $120 jacket: 30% of $120 is $36, so you pay $84. A “Buy One Get One 50% Off” on two $80 items: first at $80, second at $40, total $120 instead of $160 (25% total savings). Stacked discounts? Apply them sequentially: 20% off followed by an additional 15% off means you pay 80% × 85% = 68% of the original price (32% total savings).

Sales Tax Calculation

If your state has 8% sales tax and you buy $50 of goods, the tax is $4 (50 × 0.08), making the total $54. For reverse-calculating: if your total bill is $108 and you know the tax rate is 8%, the pre-tax amount is $108 ÷ 1.08 = $100, and the tax is $8. Use the Percentage Calculator for both forward and reverse tax calculations.

Restaurant Tips

Service Quality	Tip %	On a $60 Bill
Standard	15%	$9.00
Good	18%	$10.80
Excellent	20%	$12.00

Quick mental trick: 10% is easy (move decimal left), then double it for 20%, or add half for 15%. For exact amounts, the Tip Calculator handles split bills and custom percentages too.

Commission and Earnings

If you earn 5% commission on a $10,000 sale, your commission is $500. For real estate agents earning 3% on a $350,000 house: $10,500 commission. Sales targets: if you need to make $50,000 in commission at 8% rate, you need $625,000 in sales (50,000 ÷ 0.08).

Grade Calculations

A final exam worth 40% of your grade with a current grade of 82%: to calculate what you need on the final for an overall 90%, use weighted percentage formulas. Or simply add up the weighted scores: (82 × 0.6) + (final_score × 0.4) = desired_grade.

Common Percentage Mistakes

Adding percentages incorrectly: A 10% discount followed by another 10% is NOT 20% off — it is 19% off (100 × 0.9 × 0.9 = 81)
Confusing percentage points with percent: A rate going from 4% to 6% is a 50% increase (2 percentage points)
Misapplying reverse percentages: If a price after 20% off is $80, the original is $100, not $96 ($80 ÷ 0.8 = $100)

For instant answers to all these scenarios and more, use the Percentage Calculator at Today Calculator. It handles percentage calculations, increases, decreases, and differences in both directions.