Sales and discounts are everywhere — seasonal events, coupons, flash sales, loyalty rewards, bulk pricing. The question "how much am I actually saving?" should have a simple, instant answer.
Once you understand the underlying maths, you can verify any discount mentally. Useful when a tag shows "was £89.99, now £64.99" and you want to know if the 28% claim is accurate.
Calculate Any Discount Instantly
Discount Calculator
Find discounted price and savings from a % off.
The Core Discount Formulas
Final Price = Original Price × (1 − Discount% ÷ 100)
Savings Amount = Original Price × (Discount% ÷ 100)
Discount % = (Savings ÷ Original Price) × 100
Example: 30% Off a £120 Item
- Savings = £120 × 0.30 = £36
- Final Price = £120 − £36 = £84
- Or directly: £120 × 0.70 = £84
Working Backwards: Finding the Original Price
If you only see the sale price and the discount percentage:
Original Price = Sale Price ÷ (1 − Discount% ÷ 100)
Example: Sale price is £63, discount is 30% → £63 ÷ 0.70 = £90 original
Useful to verify whether a retailer's stated "original price" is accurate.
Finding the Discount Percentage
If you know original and final price but not the percentage:
Discount % = ((Original − Sale) ÷ Original) × 100
Example: Was £150, now £112.50 → ((150 − 112.50) ÷ 150) × 100 = 25% off
Stacked Discounts: The Common Mistake
Two sequential discounts do not simply add up.
- Original price: £200
- After 20% off: £200 × 0.80 = £160
- After additional 10% off: £160 × 0.90 = £144
- Effective discount: (200 − 144) ÷ 200 = 28%, not 30%
Two sequential discounts of x% and y% give an effective total of (x + y − xy/100)%.
Common Discount Scenarios
| Scenario | Calculation |
|---|---|
| 20% off £75 | £75 × 0.80 = £60 |
| 15% coupon on £67.50 cart | £67.50 × 0.85 = £57.38 |
| 50% off then 10% off | 50% off first → then multiply by 0.90 |
| BOGOF on £40 items (2 bought) | Pay £40 for two → £20 each |
How to Calculate 20% Off in Your Head
Move the decimal one place left to get 10%, then double it for 20%.
- £85 → 10% = £8.50 → 20% = £17 savings → final price £68
- £120 → 10% = £12 → 20% = £24 savings → final price £96
Spotting Misleading Discount Claims
Inflated "original" prices — A "was" price must reflect the actual selling price during a meaningful prior period (regulated in the UK and EU). A price that was never genuinely charged at the higher level makes the discount misleading.
"50% more free" ≠ 50% off — Getting 50% more product for the same price = 33% effective discount per unit (0.5 ÷ 1.5 = 33.3%).
BOGOF vs 50% off — BOGOF only gives 50% per item if you actually want two. If you buy one, there's no saving.
Business Use: Margin Impact of Discounts
If a product costs £40 to make and sells at £100 (60% gross margin), a 20% discount drops the price to £80. New gross margin = (80 − 40) ÷ 80 = 50%. A 20% price discount costs 10 margin points.
To break even on a discount, volume must increase. If your margin is 40% and you cut 10%, you need 33% more sales volume just to maintain the same profit.
Privacy Note
FluxToolkit's discount calculator runs entirely in your browser. The prices and percentages you enter are never transmitted to our servers or stored in any form.
Frequently Asked Questions
How do I work out the original price from a sale price?
Divide the sale price by (1 minus the discount rate). Sale price £70, 30% off: £70 ÷ 0.70 = £100.
Do discounts apply before or after tax?
Discounts apply to the pre-tax price. Tax is then calculated on the discounted selling price.
Is a 50% discount the same as half price?
Yes, exactly. 50% off means you pay 50% of the original = half price.
How does a stacked discount work?
Each discount applies to the price after the previous one. 20% off, then 10% off = 28% total, not 30%.
Does FluxToolkit store the prices I enter?
No. All calculations happen in your browser. Nothing is sent to our servers.
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