CalcThai
calcthai.com · Discount Calculator
General & conversion
Discount Calculator
Work out the price after a discount, reverse a sale price into a percentage, and decode stacked discounts: 50% off plus a further 10% is really 55% off, not 60%.
This price at each common discount
| Discount | You pay | You save |
|---|---|---|
| 5% | 950.00 | 50.00 |
| 10% | 900.00 | 100.00 |
| 15% | 850.00 | 150.00 |
| 20% | 800.00 | 200.00 |
| 25% | 750.00 | 250.00 |
| 30% | 700.00 | 300.00 |
| 40% | 600.00 | 400.00 |
| 50% | 500.00 | 500.00 |
| 60% | 400.00 | 600.00 |
| 70% | 300.00 | 700.00 |
| 80% | 200.00 | 800.00 |
| 90% | 100.00 | 900.00 |
Ask about this page
The AI assistant answers only questions about the calculator on this page.
Sale signs have a few reliable ways of looking bigger than they are, and the most effective is the stacked discount: "50% off, plus a further 10%" reads as 60% off, but it is 55%. This page works out sale prices, reverses a price into a percentage, and unpicks stacked discounts before you pay.
How it works
A single discount. Sale price = full price × (1 − discount ÷ 100). So 1,000 baht at 30% off is 700 baht, saving 300.
Reversing a price into a percentage. Discount = (full − sale) ÷ full × 100. From 1,290 down to 990 is 23.3% off — useful for comparing shops that write their offers differently.
Stacked discounts — the common trap. "50% off plus a further 10%" is not 60% off, because the second discount applies to what is left after the first.
Walk it through: 1,000 baht, 50% off leaves 500. A further 10% takes off 10% of 500 — that is 50 — leaving 450. The combined discount is 55%, not 60%. The gap is 50 baht on every thousand.
The shortcut: combined = 100 − (100 − first) × (100 − second) ÷ 100. The bigger the two numbers, the wider the gap between how it feels and what it is: 50% + 50% feels free but is 75% off.
Why shops write it this way. "55% off" looks weaker than "50% + 10%" even though they are identical. Signs like that are legal as long as the terms are clear — but a buyer who can do this arithmetic compares prices across shops far more accurately.
Mind the base. A 30% rise after a 30% cut does not return to the original: 1,000 cut to 700, then up 30% is 910, because the base changed. The same principle is why stacked discounts cannot simply be added.
Frequently asked questions
Is 50% off plus a further 10% the same as 60% off?
No — it is 55%. On 1,000 baht, 50% off leaves 500, and a further 10% of 500 is 50, so you pay 450. A true 60% discount would mean paying 400. The sign implies 50 baht more of discount per thousand than you get.
From 1,290 down to 990 — what percent off is that?
23.3%, from (1,290 − 990) ÷ 1,290 × 100. Converting prices into percentages is the reliable way to compare offers across shops that write their signs differently.
Does it matter whether VAT is added before or after the discount?
The final amount is the same either way, because both steps are multiplications. But a correct Thai tax invoice shows the discount first and charges VAT on the reduced amount.
Is 70% off applied twice the same as free?
No — you still pay 9% of the full price. The second 70% applies to the remaining 30%, leaving 30% × 30% = 9%. Stacked discounts can never reach 100% unless one layer is itself 100%.
Sources
Rates last verified 5 Sep 2026