Percentage Off + GST Calculator

This calculator applies a percentage discount and handles 15 percent GST in a single step, sorting out the order-of-operations confusion that trips people up when a sale price and GST both come into play. It is a common situation in New Zealand retail and trade: a product has a price, there is a discount to apply, and GST is either already included in the ticket price, as it is for consumers, or needs to be added on top, as it is on a GST-exclusive trade or wholesale price. Getting the sequence right matters, because applying GST before or after the discount, or forgetting that a consumer price already contains GST, leads to the wrong number. This tool removes the guesswork. You enter the original price, the discount percentage, and whether the price is GST-inclusive or GST-exclusive, and it returns the final price you pay, the dollar value of the discount, and the GST component. When the price is GST-inclusive, the discount is applied to the ticket price and the GST already inside the discounted price is shown, which is three twenty-thirds of it. When the price is GST-exclusive, the discount is applied first and then 15 percent GST is added to reach the final price. Use it to work out a sale price, to check a discounted invoice, to separate the GST for an expense claim or a return, or to compare a consumer price with a trade quote. The result always reconciles: the final price equals the discounted base plus or including the correct GST. This is an exact calculation, so you can rely on it for pricing, claims and checking receipts.

For consumer (GST-inclusive) prices the discount is applied to the ticket price. For trade (exclusive) prices, GST is added after the discount. An exact calculation.