Discount Calculator — Australia
Quick check — see the price after a percentage discount.
Calculate Australian sale prices, find the percentage off, or reverse the original price. Includes GST-inclusive totals, stacked markdowns, and bulk quantity pricing.
Australia Discount Notes
Australian discount pricing usually starts from GST-inclusive shelf prices, so shoppers and businesses often want both the sale total and the GST portion after the markdown.
This version is tailored to Australian retail maths, where stacked percentage discounts, GST extraction, and bulk quantity checks are common.
Australian version note: this discount keeps the calculation anchored to AUD amounts, local product names, Australian tax language, and the way banks, employers, agencies, or advisers usually describe the inputs.
Local cues stay visible where they matter: ATO, PAYG, superannuation, Medicare levy, stamp duty, kilometres, comparison rate, APRA, Centrelink, GST, and Australian-dollar results are not rewritten into overseas vocabulary.
Use the output as an Australian estimate first, then sanity-check it against local quotes, lender criteria, government thresholds, state rules, or professional advice before relying on the number.
Results update instantly. Stacked discounts multiply — not add.
In Australia, GST (10%) is included in almost all retail prices. Discounts are applied to the GST-inclusive price.
Discounts in Australia are applied to the full GST-inclusive price. A $200 price tag includes $18.18 of GST ($200 / 11). After a 25% discount: sale price = $150, which includes $13.64 of GST. The GST amount drops with the discount.
To find GST in a GST-inclusive price: divide by 11. To find ex-GST price: multiply by 10/11 (or divide by 1.1). To add GST to an ex-GST price: multiply by 1.1. Use Standard mode to see the full breakdown on any discounted price.
Some items are GST-free in Australia: fresh food, medical supplies, some educational materials. If the item you’re discounting is GST-free, select “Not applicable” in the GST field — the sale price calculation remains the same but no GST breakdown is shown.
Stacked discounts multiply, not add. “30% off then extra 15% off” does not equal 45% off.
Two discounts applied sequentially: (1 − 30%) × (1 − 15%) = 0.70 × 0.85 = 0.595. You pay 59.5% of the original price. Effective discount = 40.5%, not 45%. The second discount is applied to the already-reduced price, not the original.
“Extra 15% off all sale items” sounds generous but the 15% is applied to the already-reduced price. On a $500 item at 30% off ($350), the extra 15% saves $52.50 — not $75. Use Detailed mode to model any combination of stacked discounts.
Mathematically, the order of applying two discounts makes no difference to the final price. 30% then 15% = 15% then 30% = 40.5% effective discount either way. Where order does matter: if a fixed dollar discount is applied (e.g. $20 off after % discount), apply the % first.
Australian consumer law (ACCC) has specific rules about how retailers can advertise discounts.
The “was” price in a “was $X, now $Y” tag must have been a genuine price at which the item was sold for a reasonable period. Retailers cannot inflate a “was” price to make a discount appear larger. If you suspect a fake “was” price, report it to the ACCC.
If a retailer says “up to 70% off”, only one item needs to be 70% off — most items can be a much smaller discount. The ACCC requires that the most prominent discount claim is not misleading. “Up to X% off” claims are often used strategically to attract customers.
If an item scans at a higher price than displayed, you are entitled to the lower price under the Scanning Code of Practice (most major retailers). If you paid more than the advertised discount price, you can request a refund for the difference. Keep receipts for price comparison.
Three discount formulas — sale price, discount %, and original price
| Calculation | Formula & example |
|---|---|
| Sale price | Original × (1 − Discount%) → $200 × 0.75 = $150 (25% off) |
| Discount % | (Original − Sale) / Original × 100 → ($350 − $280) / $350 × 100 = 20% |
| Original price | Sale / (1 − Discount%) → $180 / 0.75 = $240 (was 25% off) |
Quick mental discount calculations for common percentages
| Discount | Mental shortcut |
|---|---|
| 10% off | Move decimal left one place → $250 × 10% = $25 saving → $225 |
| 20% off | Divide by 5, subtract → $300 ÷ 5 = $60 saving → $240 |
| 25% off | Divide by 4, subtract → $200 ÷ 4 = $50 saving → $150 |
| 50% off | Simply halve the price → $180 ÷ 2 = $90 |
| 30% off | 10% × 3, subtract → $200 × 10% = $20 × 3 = $60 off → $140 |
| 15% off | 10% + half of 10% → $200: 10% = $20, half = $10; total = $30 off → $170 |
How GST (10%) interacts with discounts on Australian retail prices
Discounts are on GST-inclusive prices
Almost all retail price tags in Australia include GST. Discounts are applied to the full GST-inclusive price. The discounted sale price also includes GST, just at a proportionally smaller amount.
| Price point | GST breakdown |
|---|---|
| $200.00 original (incl. GST) | GST = $18.18 · Ex-GST = $181.82 |
| $150.00 sale (25% off) | GST = $13.64 · Ex-GST = $136.36 |
| $100.00 sale (50% off) | GST = $9.09 · Ex-GST = $90.91 |
To extract GST from any GST-inclusive price: divide by 11. To add GST to an ex-GST price: multiply by 1.1.
How stacked discounts work — and why 30% + 15% ≠ 45%
When two discounts are applied sequentially, they multiply — not add. The second discount applies to the already-reduced price, not the original. This means the combined effective discount is always less than the sum of the two rates.
| Discount combination | Effective combined rate |
|---|---|
| 20% + 10% | 28% effective → (1-0.20) × (1-0.10) = 0.72 → 28% off |
| 30% + 15% | 40.5% effective → (1-0.30) × (1-0.15) = 0.595 → 40.5% off |
| 50% + 20% | 60% effective → (1-0.50) × (1-0.20) = 0.40 → 60% off |
❓ Frequently askedFrequently asked questions
How do I calculate a discount percentage?
Discount % = (Original price − Sale price) / Original price × 100. Example: original $200, sale $150. Discount = $50 / $200 × 100 = 25%. Use the “Find discount %” mode in this calculator to do this automatically.
Do stacked discounts add up?
No. Stacked discounts multiply, not add. “30% off then extra 15% off” does not equal 45% off. The effective combined discount is (1 − 0.30) × (1 − 0.15) − 1 = 40.5%. The second discount is applied to the already-reduced price.
Does GST apply to discounted prices in Australia?
Yes. In Australia, discounts are applied to the GST-inclusive price. The discounted sale price still includes GST at 10%. To find the GST in any GST-inclusive price, divide by 11. Use Standard mode in this calculator to see the full GST breakdown.
Can I find the original price if I only know the sale price?
Yes. Original price = Sale price / (1 − Discount%). Example: paid $180 after 25% off. Original = $180 / 0.75 = $240. Use the “Find original price” mode in this calculator.
What are the ACCC rules on discount advertising?
The “was” price in a “was $X, now $Y” advertisement must be a genuine previous price at which the item was sold for a reasonable period. Retailers cannot inflate a reference price to create the appearance of a larger discount. Report misleading discount advertising to the ACCC at accc.gov.au.