Discount Calculator — Australia
The sale price after a percentage discount — or the discount from two prices, or the original price from the sale price — with tax, quantity, a second stacked discount and a bulk break at the deeper levels.
Sale price = original × (1 − discount).
How the discount calculator works
Sale price = original × (1 − discount). Given the original and sale prices, the discount is the saving over the original; given the sale price and the percentage, the original is the sale price ÷ (1 − discount). A stacked discount applies to the sale price, not the original, which is why two 10% discounts are 19%, not 20%.
Formula: Sale = Original × (1 − d) · d = (Original − Sale) ÷ Original · Original = Sale ÷ (1 − d)
Australia Discount Notes
| 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.
Where these figures come from
Business figures on this page are drawn from the Australian Taxation Office (business tax, GST, PAYG), Business.gov.au (the federal business registration hub), Fair Work (employer obligations), and ASIC (company and director rules).
- Company tax rate (25% / 30%) — ATO — Company tax rates.
- GST rules (10%) — ATO — GST.
- PAYG withholding & employer obligations — ATO — PAYG withholding.
- Business registration (ABN/ACN) — Business.gov.au.
- Employer pay & award obligations — Fair Work Ombudsman.
- Company & director rules — ASIC — Companies.
Last checked: July 2026. Rates and thresholds are reviewed against the source of record each November, when annual adjustments for the following tax year are published.
Understanding your resultSelect the question that matches where you are right now.
The discounted price shows what you pay after the percentage reduction. Simple — but useful for comparing deals and stacking multiple discounts.
How to compare dealsCompare the dollar saving across items. A 30% discount on $50 saves less than 15% on $200.
Stacking discountsMultiple discounts compound differently. 20% then 10% off is 28% total, not 30%.
AccuracyAll calculations run entirely in your browser. The calculator code does not submit your figures to GlobalCalc to obtain a result.
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| Inputs | Sale price | Note |
|---|---|---|
| 25% off an item priced at 200 | $150.00 | sale price 150, you save 50 |
| What discount takes 200 down to 150? | $150.00 | 25% |
| Original price from a sale price of 150 at 25% off | $150.00 | 200 |
The sources behind this calculator
- Corporate Finance Institute — EBITDA — why EBITDA is a non-GAAP measure with no single definition
- US SEC — Non-GAAP Financial Measures, Compliance & Disclosure Interpretations — the disclosure rules that exist precisely because EBITDA is not standardised
- Australian Securities and Investments Commission — the Australian corporate regulator
Last checked: September 2026. These are standard management-accounting definitions; where a term has no single agreed definition, the page says so.