Discount Calculator
Compute the final price after a discount, how much you save, and the effective percent off. Choose between percent-off and fixed-amount-off modes; HK-style preset buttons (七折 / 八折 / 半價) and a sales-tax field included for shoppers outside HK.
Enter the percent taken OFF the original price — e.g. a "30% off" sale = 30.
Please enter a valid number
Final price
HK$623
You save
HK$267
Breakdown
- Original
- HK$890
- Discount (−)
- −HK$267
- Subtotal after discount
- HK$623
- Sales tax (+)
- HK$0
- Final price
- HK$623
Hong Kong retail labels work the opposite way to Western ones — "七折" means "pay 70%", i.e. 30% off. This tool uses "percent off" as the standard input.
Formula
Discount = Original × Percent off Subtotal = Original − Discount Final = Subtotal × (1 + Sales tax %) Savings = Original − Subtotal
- · Hong Kong retail labels work the opposite way to Western ones — "七折" means "pay 70 %", i.e. 30 % off. The tool uses percent-OFF as the standard input; preset buttons map the HK labels for you.
- · Sales tax / VAT is normally charged on the discounted subtotal, not the original price. Hong Kong has no sales tax — set 0; for the US, UK or EU, enter the local rate (e.g. UK VAT 20 %, NYC sales tax 8.875 %).
- · Stacked discounts multiply, they do not add — "10 % member discount on top of 20 % off" = 100 % × 80 % × 90 % = 72 %, which is 28 % off, not 30 %.
- · If a fixed amount off is larger than the original price, the tool caps it at the original — final price will never go below zero.
- · Reverse calculation: if you only know the sale price and percent off, original price = sale ÷ (1 − percent off).
- · Price math only — shipping, handling fees, membership dues and any service charges added later by the merchant are not modelled.
Frequently asked
How does the HK label 七折 (chat-jit) map to "percent off"?
Each 折 ("zip") = 10 % of the original. 七折 = pay 70 %, i.e. 30 % off; 八折 = pay 80 %, i.e. 20 % off; 半價 = pay 50 %, i.e. 50 % off. The shortcut: (number before 折) × 10 = percent you pay, so 100 − that = percent off. The quick-preset buttons in this tool fill the right number for you.
A shop offers "10 % off, plus an extra 5 % for members" — what is the combined discount?
Stacked percentages multiply, not add — remaining fraction = 90 % × 95 % = 85.5 %, so the combined cut is 14.5 % off, not the intuitive 15 %. On a $1,000 item the member price is $855 (saves $145), not $850. If a sales rep says "discounts stack", always check whether they actually mean additive (rare) or multiplicative (the normal case).
Is sales tax charged before or after the discount?
Almost every jurisdiction levies sales tax on the discounted subtotal, i.e. tax × (subtotal after discount). That is consumer-friendly: discount first, then tax. The tool uses this standard order. The rare exception is some gift-card or coupon rules that tax the pre-discount price; if your receipt shows that, trust the receipt and adjust accordingly.
I only know the sale price — how do I back out the original?
Use: original = sale ÷ (1 − percent off / 100). Example: $640 at 20 % off → 640 ÷ 0.8 = $800. You can also dial the "Original price" field in this tool until the displayed final price matches what you know.
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