Are stacked discounts additive or multiplicative?

Always multiplicative when applied 'one after another' — a 20% off plus 10% off applied sequentially is (1−0.20) × (1−0.10) = 28% off, not 30%. The tool shows both interpretations so you can verify the shop's intent.

Why does the bigger discount seem smaller than expected?

A 50% discount halves the price; a second 50% halves it again, leaving 25% of the original. The marginal benefit of each subsequent discount shrinks because it applies to an already-discounted base.

Does sales tax apply before or after the discount?

Usually after (in the US). Discounts reduce the taxable price, so you pay less tax too. Some VAT-inclusive countries apply tax to the pre-discount price. Use the Sales Tax Calculator alongside this one.

discount · savings · stacked · local

Calculate discounts and stacks

Single percent or sequential stacks of discounts. See savings, final price, and the difference between additive vs sequential application — entirely in your browser.

Discount Calculator

Original

100.00

input

Discount

25%

rate

Savings

25.00

off

Final

75.00

to pay

input · numbers

Original priceDiscount %

Single mode: final = original × (1 − discount/100).

output · result

You save

25.00

Final price

75.00

Formula

100.00 × (1 − 25/100)

Quick Start

How discounts stack

10% then 20% off is not 30% off — it's 28% off because the second discount applies to the already-reduced price.

01
Pick mode
Single percent or stack of multiple discounts.
Inputs are treated as UTF-8 throughout the pipeline and validated client-side as you type — nothing dispatches until the value is well-formed.
modeinpututf-8client-sidevalidated
mode · textstack · set
```
10, 15, 5
```
loaded · parsedclient-side
02
Enter price
The original / list price.
Each toggle re-computes through a memoised hook, so flipping options never resets your input and the UI stays snappy on large inputs.
priceoptionslivememoisedtoggles
price · memoised$100 · live
```
$100.00
```
options set · memoisedlive
03
Enter discounts
Single value or comma-separated stack.
Randomness — where used — comes from crypto.getRandomValues, never Math.random. Heavy work sits in useMemo.
pctcomputeinstantlocaldeterministic
pct · instantstack · computed
```
10, 15, 5
```
computed · instantinstant
04
Read both totals
Additive sums percentages; sequential compounds. Sequential is usually the legal interpretation.
Copy writes through navigator.clipboard and downloads use a Blob — zero network traffic. Same input plus same options always yield the same bytes.
readcopydownloadzero-networkreproducible
ok · copiedready · copied
```
Copied
```
shipped · ready to shipsuccess

Pro tips

Pro tips for everyday utilities

Reach for crypto.getRandomValues

Cryptographically random for IDs, tokens, salts. Math.random is for animation and games, not security.

Sort IDs lexicographically

UUID v4 has no time ordering. Use ULID or UUID v7 if you need sorted IDs.

Mock data with seeds

Faker-style libraries can be seeded so tests are reproducible. Embed the seed in the fixture file.

Reference cards beat memory

Cheatsheets for Vim, Git, Docker, Linux signals are faster than man pages when you’re mid-flow.

Browser APIs vary

Touch events, gamepads, and clipboard differ across vendors. Feature-detect before use.

Persist in the right place

localStorage for user preferences, sessionStorage for transient state, IndexedDB for structured data.

Use Cases

When to compute discounts

Sales, promo codes, B2B contracts.

Black Friday math

Compare 30% off vs 15+15 stack. Random values come from crypto.getRandomValues — cryptographically secure for tokens, salts, and session IDs. Math.random is deterministic enough for animations but predictable enough to be a security bug.

CSPRNG-backed

Coupon stacking

See what sequential codes really save you. Pair with hashids, ULID, or UUID v7 when you need both random and sortable — useful for primary keys, public-facing IDs, and event log ordering without a sequence column.

reproducible

B2B pricing

Volume + loyalty discounts compounded. Output is deterministic given the same seed, so fixtures and tests stay reproducible across CI runs and contributor machines. Embed the seed in the fixture file for full replay.

b2b

Margin checks

Verify deal margins before approval. Heavy work runs through useMemo so the UI stays snappy on large inputs. Same input + same options yields identical bytes — the kind of stability snapshot tests rely on.

feature-detected

Quote builders

Quick sanity check when sending quotes. Storage tools persist to the right backend: localStorage for user preferences, sessionStorage for transient state, IndexedDB for structured data. Pick the right shelf and quota worries disappear.

deterministic

Comparison shopping

Apples-to-apples final price across stores. Browser feature detection: clipboard, fullscreen, gamepad, and Web Bluetooth APIs gracefully fall back when unavailable. No surprise white screens on Safari or older Firefox.

production-ready

FAQ

Frequently asked questions

Additive vs sequential?

Additive sums the percents. Sequential applies each to the previous result. Sequential is mathematically correct for stacked discounts in most jurisdictions.

Is 20+20 the same as 40?

No. 20% then 20% = 36% off (sequential). Additive would say 40% off.

What if the total exceeds 100%?

Additive caps at 100%. Sequential approaches but never quite hits 100%.

Do you handle minimum prices?

No — combine in your own logic. The calculator just shows the math.

Does it run locally?

Yes — all math is in your browser. Nothing is sent to a server.

Suggest a tool

Something missing?

Tell us what you need. We ship the top requests every two weeks.

47 in queue·8 shipped this month

Request queued. Thanks!