Percentage Off Calculator

And the volume it needs to break even.

And the volume it needs to break even. A 20% discount on a 44% margin needs 83% more units to hold contribution, not 20% more.

Written and maintained by Mohit PatelLast checked August 4, 2026How we build these

Currency

Price

Discount

Contribution margin

Discounted price

$46.40

$11.60 off

Original price$58.00

Discount$11.60

New price$46.40

Units needed to break even1.83×

A 20% discount on a 44% margin needs 83% more units to hold contribution, not 20% more. That gap is why discounts are planned against the percentage and judged against revenue.

How the Percentage Off Calculator works

A 20% discount on a 44% margin needs 83% more units to hold contribution, not 20% more. That gap between how a discount reads and what it does is why promotions are planned against the percentage and judged against revenue.

Also known as: what is 30 percent off · percent discount calculator · how much off is that · half price calculator · take percentage off

The arithmetic, and the direction people get wrong

Taking a percentage off is straightforward: multiply by one minus the discount. A 30% discount on £80 leaves £56. The reverse trips people constantly, because adding back 30% does not return you to £80. It returns £72.80.

To recover the original from a discounted price, divide rather than multiply: £56 divided by 0.7 is £80. This matters commercially when working backwards from a target sale price to a list price, which is what happens whenever a marketplace demands a specific promotional price.

The same asymmetry explains why a 50% markdown needs a 100% increase to reverse. Percentages are not symmetric around their base, and pricing decisions made as though they are lose money in one direction reliably.

What the discount does to profit

A discount comes entirely out of the margin, which means the percentage effect on profit is far larger than the percentage off the price.

Take a £50 item costing £30. Contribution is £20, or 40%. Discount 20% and the price is £40, so contribution falls to £10. A 20% discount cut the profit in half.

The general rule is that the profit reduction equals the discount divided by the contribution margin. A 20% discount on a 40% margin halves the profit. The same discount on a 25% margin removes 80% of it. Which is why identical discounts are trivial in one category and ruinous in another, and why cross-category comparisons of discounting practice are close to useless.

The volume needed to stand still

The break-even volume increase for a discount is the discount divided by the new contribution margin, and the numbers are usually startling.

On the example above, a 20% discount cutting contribution from £20 to £10 needs sales to double simply to make the same profit. Not to gain anything, just to break even on the decision.

Very few promotions double volume. Which means most discounts lose money in the period they run, and are justified on other grounds: clearing stock, acquiring customers who will return, or defending share. Those justifications may be sound and they should be stated, because a discount defended as profitable in itself usually is not.

Where percentage discounting misleads

A percentage is easy to communicate and it hides the pound amount, which cuts both ways. On a cheap item, 30% off sounds generous and saves very little. On an expensive one, 10% off sounds modest and saves a lot.

There is a well-observed rule of thumb in retail that percentage discounts read as more generous below about £100 and absolute amounts read as more generous above it. Whether that holds for your catalogue is testable and worth testing.

The other distortion is the reference price. A percentage is off something, and if the something is inflated the discount is fictional. That is both a consumer protection issue in most jurisdictions and a credibility issue with customers, who compare prices far more readily than they used to.

The reference price rules

Advertising a discount from a price you never genuinely charged is prohibited in the UK, the EU and most US states, and enforcement has increased.

The EU's Omnibus Directive requires that any announced price reduction show the lowest price applied in the previous 30 days as the reference. That rule closed the loophole where a price was raised briefly before a sale so the discount looked larger.

UK guidance under the Chartered Trading Standards Institute pricing practices code is similar in effect: the reference price has to be one the goods were genuinely offered at for a meaningful period. Sellers running permanent sales from a nominal list price are exposed, and the exposure has grown as regulators have started acting on it.

Where to go next

The Percentage Off question rarely arrives on its own. These are the ones that usually come with it:

Discount Margin Impact Calculator — Required volume rises steeply as margin falls.
Minimum Discount for Profit Calculator — The floor an automated discount must respect.
Dollar Off Calculator — A fixed amount shifts the mix downward.
Etsy Fee Calculator — Every Etsy fee on one sale, itemised.

Not financial advice. Marketplace fees change, and they vary by country, plan and seller status. Every rate here is an editable default, not a quoted price, check the platform's current fee schedule before you price a product against it. This is not tax or business advice.

Frequently asked questions

How do I calculate a percentage discount?

Multiply the price by the discount percentage to get the saving, then subtract. The harder question is what volume increase the discount requires to be worth doing.

How much extra volume does a discount need?

Margin divided by (margin minus discount). At 44% margin a 20% discount needs 1.83 times the units; at 25% margin the same discount needs 5 times.

Why does margin matter so much?

Because the discount comes entirely out of contribution. A thin margin means the discount consumes a large share of what each sale earns, so far more sales are needed to replace it.

When is a discount clearly worth it?

When it clears stock you would otherwise write off, when it acquires a customer who will buy again, or when the volume genuinely arrives. Discounting to existing customers who would have paid full price is a straight transfer.

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