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
| Original Price | 20% Discount | You Pay |
|---|---|---|
| $50 | $10 | $40 |
| $100 | $20 | $80 |
| $150 | $30 | $120 |
| $200 | $40 | $160 |
| $250 | $50 | $200 |
| $300 | $60 | $240 |
| $500 | $100 | $400 |
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
- Apply discount first: $100 - $20 = $80
- Calculate tax on discounted price: $80 × 0.08 = $6.40
- 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":
- Move the decimal left (10%)
- Double it (20%)
- Subtract from original price
- Done
Shop smarter, save more!
Related Articles
More Discount Percentages
Verify your math: Use our discount calculator to check any 20% off calculation instantly.
Try It Yourself
If you want to explore more tools like this, check out our full collection of online percentage calculators for everything from discounts to tax and profit margin formulas.
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