Discount calculator

How to use it

1. Enter the original price and the discount percentage.
2. The final price and the saving update instantly.
3. Add a second discount if one stacks — it applies to the reduced price, not the original.

Where tax sits in the sum, and when a coupon moves it

Multiplication commutes, so a discount then tax gives the same total as tax then the discount. What differs is which figure the shelf price already contains. UK and EU retail prices shown to consumers must include VAT, so a 20% reduction comes off a tax-inclusive number and the VAT falls with it. US shelf prices are usually pre-tax, with sales tax added at the till on the reduced amount.

Coupons break that symmetry. In several US states a retailer’s own discount reduces the taxable amount, while a manufacturer’s coupon does not, because the shop is reimbursed for the value and tax is charged on the pre-coupon price. Two reductions of the same size on the same item can therefore produce different totals depending on who is funding them.

The reference price is regulated, and multibuys need converting

The EU Omnibus Directive, in force since May 2022, requires any announced price reduction to state the lowest price the trader applied in the previous 30 days, which closes off the tactic of briefly raising a price to manufacture a deeper-looking cut. The UK did not adopt it, but trading standards guidance still expects a 'was' price to be one the item genuinely sold at, for a meaningful period rather than a fortnight.

Multibuys have to be converted into a single percentage before they can be compared with a straight reduction. Three for two is 33.3% off, not 50%. Buy one get one free is 50% off across the pair, not 100%. And 'up to 70% off' is a claim about the deepest cut in the range, which usually applies to the fewest lines on the rail.

Questions