Discount Calculator: How to Calculate Sale Price and Savings

Discounts are the single most-used percentage calculation in everyday life. They are also the calculation retailers most rely on customers getting wrong. A few minutes of basic math can save you 10–30% on most large purchases and stop you ever fleeing for the "BIGGEST SALE EVER" sign again.

The discount formula

Discount amount = Original price × (Discount % ÷ 100) Final price = Original price − Discount amount

Or in one step: Final = Original × (1 − Discount%).

Example. A $120 jacket marked 25% off. Discount = 120 × 0.25 = $30. Final price = 120 − 30 = $90.

Reverse: what % off is this?

Discount % = (Original − Sale) ÷ Original × 100

Example. Original $80, sale $58. (80 − 58) ÷ 80 = 0.275 → 27.5% off.

Stacked discounts (almost always misunderstood)

"30% off, then take an extra 20% off at checkout!" sounds like 50% off. Do the math:

• After first discount: $100 × 0.70 = $70
• After second discount: $70 × 0.80 = $56
• Total off: $44 → 44% off, not 50%

Formula: Final = Original × (1 − D1) × (1 − D2) × …

Discount + sales tax

Order matters less than you think:

• Apply discount, then tax: $100 × 0.80 × 1.08 = $86.40
• Apply tax, then discount: $100 × 1.08 × 0.80 = $86.40

Identical (multiplication is commutative). What does differ: the tax is calculated on a smaller base, so total tax paid is lower if discount is applied first — but most jurisdictions require exactly that order anyway.

Quick mental shortcuts

• 10% off → move decimal one place left, subtract. $48 → $4.80 off = $43.20.
• 20% off → 10% twice. $48 → $9.60 off = $38.40.
• 25% off → quarter price off. $48 → $12 off = $36.
• 33% off → roughly one-third. $48 → ~$16 off = $32.
• 50% off → half. Easy.
• 75% off → divide by 4. $48 → $12.

The psychology of discounts

Retailers don't price randomly. The most common tactics:

• Anchoring. Show the "original" price first, then the sale — even if nothing ever sold at the original.
• Charm pricing. $19.99 reads as "$19-something", not $20.
• Reference price inflation. Mark up by 30% before discounting 30% to claim a sale.
• Bundling. "Buy 2 get 1 free" = 33% off, but only if you wanted three.
• Deadline pressure. "24 hours only" disables careful thinking.

Defense: know the typical price before the sale starts. CamelCamelCamel (Amazon), Honey, PriceSpy and Trolley.co.uk all track historical pricing.

BOGO math

• Buy one get one free = 50% off if you wanted two.
• Buy one get one 50% off = 25% off if you wanted two.
• Buy 2 get 1 free = 33.3% off if you wanted three.

Coupon + sale combos

Some stores allow stacking; some don't. Always test the cart before committing. The order can also matter — at some retailers, a percentage coupon applied after a dollar-off coupon nets more savings than the reverse.

Frequently asked questions

Is "50% off" always genuine? Not always — many regulators require the "original price" to have been available for some period (e.g. 30 days). Suspect any price that has only ever appeared in a "sale".

How do I calculate percentage savings on multiple items? Sum the savings, divide by sum of originals.

Are loyalty points the same as discounts? Sort of — convert to cash value first. 1,000 points worth $5 on a $100 purchase = 5% effective discount.

Use our Discount Calculator to handle stacked discounts, taxes and reverse-percentages in one place.