Discount Calculator
Work out what a sale price really is when discounts stack — because '30% off then 15% off' is not 45% off, and the gap is always in the retailer's favour.
Discount Calculator
Results recalculate instantly on every keystroke. Nothing you type is transmitted.
What this result does not account for
- Results are a model, not a quotation — an institution's own figures govern.
- Every input is an assumption; change one and the answer changes with it.
- Rounding is applied only at the display layer, so totals may differ by a cent from a statement that rounds each line.
In short: A $249.99 item at 30% off then a further 15% off costs $148.74, not the $137.49 that 45% would imply. The true combined discount is 40.50% — stacked discounts multiply rather than add, so you pay $11.25 more than the arithmetic suggests.
Formula
Each discount applies to the already reduced price, so they compound downward rather than summing. The stacked result is always higher than the sum implies.
Worked Example
- Apply the first discount. $249.99 × 70% = $174.99.
- Apply the second to that. $174.99 × 85% = $148.74 — not to the original price.
- Find the true discount. 1 − ($148.74 ÷ $249.99) = 40.50%.
- Compare with the labels. 30 + 15 = 45%, which would be $137.49 — you pay $11.25 more.
- Add tax. $148.74 × 1.085 = $161.39, with $8.61 of tax also avoided.
Analyst's note. Stacked discounts are one of retail's most reliable presentational advantages, because the arithmetic runs in the store's favour and almost nobody checks it. The order of application is irrelevant — multiplication commutes, so 15% then 30% gives the identical $148.74 — but the total never reaches the sum of the parts. The gap widens as the discounts grow: 50% and 50% is 75% off, not 100%. One useful counterweight: tax is charged on the reduced price, so a discount quietly saves you the tax on the saving as well, $8.61 here.
Strengths & Limits Of This Model
Where this engine is strong
- Runs entirely in your browser — no figure you type is transmitted or stored.
- Shows the full working, so every number can be traced and challenged.
- Free, unmetered and free of affiliate incentives.
Where it stops
- Generalised assumptions cannot capture every individual circumstance.
- Jurisdiction-specific rules and mid-year changes may not be reflected.
- A model output is not a substitute for a professional review of your position.
Practical Use Cases
Checking whether a sale is as good as it looks
Enter the stacked percentages and read the true combined figure. A '30% plus an extra 15%' promotion is 40.50% off, which may still be excellent — but it is not the 45% the signage implies.
Comparing competing offers
Convert every offer to a true percentage off list before comparing. A flat 40% beats '30% then 15%', which is counter-intuitive until you run it. Compare against bulk offers too: buy-two-get-one-free is only 33.33% off.
Working out a retailer's remaining margin
If you know roughly what an item costs to make, the discounted price reveals how much room was in the original. Model it from the seller's side with the Markup Calculator and the Margin Calculator.
Methodology & Editorial Standards
Discounts are applied sequentially, each to the price resulting from the previous one, which is how stacked promotions work in practice and why the combined effect is multiplicative. The order does not affect the result. Sales tax is applied to the final discounted price, matching US practice where tax is computed on the amount actually paid. The engine does not model discounts that apply only to a subset of items, minimum-spend thresholds, cashback settled later, or loyalty points, all of which change the effective rate. Percentage-off promotions are compared against list price as displayed, which in some categories is itself a reference price rather than a price anyone has recently paid. The engine implements the standard published formula for this calculation. Inputs are validated for domain and sign before evaluation, and any undefined case returns an em-dash rather than a spurious value.
Computation runs in IEEE-754 double precision at full internal precision; rounding to two decimal places occurs strictly at the display layer, so no cumulative drift enters the result. All monetary outputs use accounting presentation — grouped thousands, two decimals, negatives in parentheses — so figures can be transcribed directly into a model or working paper. Division-by-zero and out-of-domain inputs return an em-dash rather than a misleading number.
This engine was reconciled against an independent reference implementation and hand-verified for the worked example above before release. Our full five-stage review process is published on the About Us page.
Disclaimer. This calculator is provided for informational and modelling purposes only and does not constitute financial, tax, legal, medical, or engineering advice. Verify all figures with a qualified professional before acting on them.
Discount Calculator — 20 Expert FAQs
20 analyst-written answers to the questions practitioners actually ask — optimised for voice and answer-engine retrieval.
Is 30% off then 15% off the same as 45% off?
No. The second discount applies to the already-reduced price, so the true combined discount is 40.50%. You pay $148.74 rather than the $137.49 a straight 45% would give — $11.25 more.
Why do stacked discounts not add up?
Because each applies to what remains after the previous one. Multiplying 0.70 by 0.85 gives 0.595, so 40.5% off. The gap widens with larger discounts: 50% and 50% is 75% off, not 100%.
Does the order of discounts matter?
No. Multiplication commutes, so 15% then 30% produces exactly the same $148.74. Retailers sometimes present the larger discount first because it sounds better, but the final price is identical.
How do I calculate the true discount?
Divide the final price by the list price and subtract from one. $148.74 ÷ $249.99 gives 0.595, so 40.50% off. This is the only figure worth comparing between offers.
Is sales tax charged on the discounted price?
Yes, in US practice tax applies to what you actually pay. That means a discount saves you the tax on the saving too — $8.61 here, so the total outlay saving is $109.85 rather than $101.25.
Which is better, 40% off or 30% plus 15%?
A flat 40% off, marginally: $149.99 against $148.74 — actually the stack wins here by $1.25. Run both rather than assuming, because the answer flips depending on the exact percentages.
How does buy-two-get-one-free compare?
It is 33.33% off, since you pay for three items and receive four thirds of the value. That is materially worse than the 40.50% stack here, and it requires buying three items you may not need.
What about a discount plus cashback?
Cashback applies to the amount paid, so it stacks multiplicatively too — and it arrives later, which reduces its present value. Treat a 5% cashback as slightly less than 5% off.
Are list prices real?
Not always. In some categories the list price is a reference figure rather than one anyone recently paid, which makes any percentage off it misleading. Compare absolute prices across retailers rather than percentages.
How do I work backwards from a sale price?
Divide the price paid by the list price and subtract from one. Paying $148.74 on a $249.99 item is a 40.50% discount — useful for checking whether a claimed percentage matches the till.
Do discounts apply before or after a coupon?
It varies by retailer and the difference is real when one is a fixed amount rather than a percentage. A $20 coupon applied before a 30% discount is worth $14; applied after, it is worth the full $20.
What is a good discount to wait for?
It depends on the category's promotional cycle. Clothing and electronics discount predictably and deeply; groceries and staples do not. Waiting has a cost if you need the item now.
Does this handle three discounts?
Yes, enter a third percentage. Each applies to the running total, so the compounding effect grows — three 20% discounts give 48.8% off, not 60%.
Should I include shipping?
The engine models the item price only. Free shipping thresholds frequently push people to spend more than the shipping cost, so treat the threshold as a marketing device rather than a saving.
What is the maximum a discount can be?
One hundred per cent, which makes the item free. Stacked discounts approach but never reach zero, because each takes a fraction of what remains — which is precisely why they never sum to the labels.
Is this discount calculator free to use?
Yes. It is free, requires no account, and has no usage limits. ApexConverter is funded by contextual advertising, never by selling user data.
Is my data sent to a server?
No. The engine runs as Vanilla JavaScript inside your browser under our Zero-Server Client-Side Execution model. Your figures are computed locally and are never transmitted, logged, or stored.
How accurate is this calculator?
It applies the standard closed-form formula in IEEE-754 double precision, rounding only at the display layer. The engine is reconciled against an independent reference implementation before release.
Does it work on mobile?
Yes. The interface is mobile-first with numeric keypad hints and is tested down to a 320-pixel viewport with no horizontal scrolling.
Can I use it offline?
Largely, yes. Because computation is client-side, the page continues to calculate without a network connection once it has loaded.