How to Calculate 20% Off: Complete Step-by-Step Guide with Examples

The Simple Formula for 20% Off

Discount Amount = Original Price × 0.20
Final Price = Original Price - Discount Amount

Or the shortcut:

Final Price = Original Price × 0.80

When something is 20% off, you pay 80% of the original price. That's it.

Real-World Examples

Example 1: $100 Item with 20% Off

• Original price: $100
• Discount (20%): $100 × 0.20 = $20
• Final price: $100 - $20 = $80
• You save: $20

Example 2: $75 Jacket with 20% Off

• Original price: $75
• 20% of $75: $75 × 0.20 = $15
• Final price: $75 - $15 = $60
• You save: $15

Example 3: $250 Electronics with 20% Off

• Original price: $250
• Discount amount: $250 × 0.20 = $50
• Final price: $250 - $50 = $200
• You save: $50

Example 4: $39.99 Online Purchase with 20% Off

• Original price: $39.99
• Discount: $39.99 × 0.20 = $8.00
• Final price: $39.99 - $8.00 = $31.99
• You save: $8.00

Mental Math Trick: The 10% Method

You don't need a calculator. Use this simple trick:

Step 1: Find 10% (move decimal one place left)

• 20% off $100? 10% = $10
• 20% off $250? 10% = $25
• 20% off $89? 10% = $8.90

Step 2: Double it (because 20% = 2 × 10%)

• $10 × 2 = $20 discount
• $25 × 2 = $50 discount
• $8.90 × 2 = $17.80 discount

Step 3: Subtract from original

• $100 - $20 = $80
• $250 - $50 = $200
• $89 - $17.80 = $71.20

Quick Reference: $20 Off Common Prices

Common Shopping Scenarios

Black Friday: "20% Off Everything"

You're at a store and see "20% off all items."

• Sweater originally $60? Pay $48 (save $12)
• Shoes originally $120? Pay $96 (save $24)
• Jeans originally $80? Pay $64 (save $16)

Online Coupon: "SAVE20"

You found a 20% off coupon code online.

• Cart total: $175
• Discount: $175 × 0.20 = $35
• You pay: $140 instead of $175

Loyalty Discount: "Members Get 20% Off"

You're a store member getting 20% off your purchase.

• Groceries normally $85? You pay $68 (save $17)
• Electronics normally $300? You pay $240 (save $60)

What Happens With Tax After the Discount?

Important: Tax applies AFTER the discount.

Scenario: $100 item, 20% off, 8% sales tax

1. Apply discount first: $100 - $20 = $80
2. Calculate tax on discounted price: $80 × 0.08 = $6.40
3. Final total: $80 + $6.40 = $86.40

Use our discount calculator to instantly verify any 20% off calculation, or our tax calculator to add tax to your final price.

Common Mistakes to Avoid

Mistake 1: Calculating Tax Before Discount

❌ Wrong: $100 + 8% tax = $108, then 20% off = $86.40 ✅ Correct: 20% off $100 = $80, then + 8% tax = $86.40

(Same answer in this case, but order matters conceptually)

Mistake 2: Thinking Multiple 20% Discounts Stack

❌ Wrong: 20% off twice = 40% off total ✅ Correct: 20% off, then 20% off again = 36% off total

Why? The second 20% applies to the reduced price, not original.

Mistake 3: Forgetting About Rounding

When calculating 20% of prices like $37:

• $37 × 0.20 = $7.40 (exact)
• Don't round to $7 and lose the 40 cents

Quick Tools

• Discount Calculator - Calculate any percentage off instantly
• Percentage of a Number - Find exact discount amounts
• Tax Calculator - Add tax after your discount

All are free and work on your phone while shopping.

The Bottom Line

20% off is simply paying 80% of the original price. Use the 10% method to calculate it in your head, or use our calculator to verify. Either way, you'll never overpay again.

Next time you see "20% off":

1. Move the decimal left (10%)
2. Double it (20%)
3. Subtract from original price
4. Done

Shop smarter, save more!

Related Articles

• How to Calculate Tips
• Black Friday Discount Guide
• Discount Stacking Explained

More Discount Percentages

• How to Calculate 10% Off
• How to Calculate 25% Off
• How to Calculate 50% Off

Verify your math: Use our discount calculator to check any 20% off calculation instantly.