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Discount Calculator

Calculate sale price with stacked discounts and optional tax. Reverse mode finds the original price from a sale price.

Final price
$75.00
You save $25.00

Applied to the discounted price

Final price
$75.00
You save $25.00 (25.0%)
Discount amount
$25.00
Price after discount
$75.00
You save
$25.00

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    Each calculator is unit-tested against authoritative sources.

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How to use the Discount Calculator

  1. 1

    Enter your inputs

    Fill in the required fields at the top of the discount calculator. Each input shows a default placeholder so you can see the expected format and units before you type.

  2. 2

    Adjust assumptions and options

    Use the toggles, sliders and dropdowns to tailor the calculation to your situation — currency, country, time period, advanced options and any optional fields all change the result in real time.

  3. 3

    Review the result

    The result card updates instantly as you type. Read the headline number, then check the breakdown, chart and any per-period schedule to understand how the inputs combined to produce the answer.

  4. 4

    Compare scenarios

    Change one input at a time to see how sensitive the result is to that variable. This is how you build intuition: small changes that move the answer a lot are the levers that matter.

  5. 5

    Share or save your result

    Copy the shareable link to send the exact scenario to someone else, or use your browser to print or save the page. The URL preserves every input so the recipient sees the same answer you do.

What this calculator does

A discount is a reduction from a stated price, expressed either as a percentage (20% off) or as an absolute amount ($10 off). The discount calculator converts between original price, discount rate and sale price in either direction. When multiple discounts apply (e.g., 30% off store sale plus an extra 15% off with a coupon), they almost always stack multiplicatively: the second discount applies to the already-reduced price, not the original. So 30% + 15% stacked = 1 - 0.7 * 0.85 = 40.5% total off, NOT 45%. This is the single most common discount math error - shoppers expect the discounts to add, retailers apply them multiplicatively, and the difference is real money. The calculator handles all of this exactly.

Formula

Sale Price = Original * (1 - d1) * (1 - d2) * ... * (1 - dn), with Tax = Sale * (1 + t)
Original
Original list price before any discount
d1, d2, ...
Each discount rate as a decimal (20% = 0.20)
Sale Price
Final price after all discounts
t
Sales tax rate as decimal (e.g., VAT 20% = 0.20)
Savings
Original - Sale Price (amount saved)

Discounts stack multiplicatively, not additively. The reverse calculation, finding the original price from a known sale price, is Original = Sale / (1 - d) for a single discount, or Original = Sale / [(1 - d1) * (1 - d2)] for stacked. Sales tax is applied after all discounts because tax is computed on the actual transaction amount, not on the pre-discount list price (true in nearly all VAT, GST and US state sales tax systems).

Worked examples

Example: $120 jacket, 30% off

Original price = $120, discount = 30%.

Sale price = 120 * (1 - 0.30) = $84 You save = $36

If sales tax is 8.25% (e.g., California), the final amount charged at checkout = 84 * 1.0825 = $90.93. Tax is calculated on the post-discount $84, not on the original $120 - this is the standard rule everywhere except some specialty taxes (e.g., certain luxury or excise taxes).

Example: stacked discounts (30% off + 15% coupon)

Original price = $200, store sale = 30% off, member coupon = additional 15% off.

A common mistake: assuming 30% + 15% = 45% off, giving $110. Actual stacked discount calculation: 200 * (1 - 0.30) * (1 - 0.15) = 200 * 0.70 * 0.85 = $119 Effective total discount = 1 - 0.70 * 0.85 = 40.5%, not 45%

You save $81, not $90. The $9 difference is exactly the additive-vs-multiplicative gap and is real money you walk out without.

Example: reverse calculation - finding the original price

You see a jacket marked "30% off - $89". What was the original price?

Original = Sale / (1 - discount) = 89 / (1 - 0.30) = 89 / 0.70 = $127.14

You're saving $38.14. This is useful for spotting fake discounts - if the "original" stated price is suspiciously round vs the sale price, the original might have been inflated specifically to make the sale look bigger.

Common use cases

  • Comparing the real cost of two competing offers (50% off + 10% coupon vs straight 55% off)
  • Calculating the total savings on a multi-item shopping cart with mixed discounts
  • Working out what the original price was when a retailer only shows the sale price
  • Pricing your own products with a target margin after a planned discount campaign
  • Black Friday / Cyber Monday shopping math - especially when "extra X% off already-reduced prices" is involved
  • Calculating final checkout amount with multi-state sales tax for US shoppers
  • B2B procurement - applying volume discount + early-payment discount + cash discount in stacked sequence

What affects the result

  • Whether discounts are stacked multiplicatively (almost always) or additively (almost never)
  • Whether sales tax is applied pre-discount (rare, e.g., some excise/luxury rules) or post-discount (standard)
  • Whether the discount is on the marked price or the membership/loyalty price
  • Coupon exclusions - clearance, sale items, gift cards, and certain brands are often excluded from extra-coupon stacks
  • Discount stacking order - usually doesn't matter mathematically because multiplication is commutative, but the receipt may show different line items
  • Tax-inclusive vs tax-exclusive pricing (Europe/UK typically inclusive; US typically exclusive)
  • Free shipping thresholds - a "free shipping over $50" rule can make a $48 cart cheaper to bump to $50 than to keep at $48

Tips

  • Use a calculator (this one!) for stacked discounts - mental math nearly always overstates the savings
  • Check the unit price, not just the percent off - bigger packs aren't always cheaper per unit even with a discount
  • Stack a manufacturer coupon, a store coupon and a credit card cashback for the deepest legitimate discount
  • Wait for predictable sale events - Black Friday, end-of-season, post-holiday clearance routinely beat random "flash sales"
  • Use price-tracking tools (camelcamelcamel for Amazon, Honey, Keepa) to verify the "original" price wasn't inflated days before the sale
  • Apply discounts in the highest-percent-first order at checkout if the system lets you choose (often it doesn't matter, but psychologically reads better)
  • For B2B, negotiate the discount as a percentage of net (post-other-discount) price, not list price - it's actually a bigger discount in dollars
  • Always factor tax and shipping into total cost before comparing offers

Mistakes to avoid

  • Adding stacked discount percentages instead of stacking them - 30% + 15% = 40.5%, not 45%
  • Calculating sales tax on the pre-discount price - tax is on the actual transaction amount
  • Trusting inflated "original" prices - if the retailer never actually sold at the original price, the discount is fictional
  • Forgetting shipping and handling - a 50% off product with $20 shipping can cost more than a 30% off competitor with free shipping
  • Ignoring loyalty program points/cashback - 2% back on $100 is functionally an extra 2% discount
  • Buying on sale that you wouldn't have bought at full price - 70% off something you don't need is 100% wasted money
  • Not checking unit price - a "buy 2 get 1 free" deal on a $30 item is 33% off, not 50% off

Frequently asked questions

How do I calculate a discount?

Multiply the original price by (1 - discount rate). For 25% off a $80 item: 80 * (1 - 0.25) = 80 * 0.75 = $60. The savings = original - sale = $20. Alternatively, savings = original * discount rate.

How do stacked discounts work?

Stacked discounts multiply, not add. A 30% sale plus a 20% coupon = 1 - (0.70 * 0.80) = 44% total off, NOT 50%. Apply each discount sequentially: $100 -> $70 (30% off) -> $56 (additional 20% off). Order doesn't matter mathematically because multiplication is commutative.

Does sales tax apply before or after the discount?

After the discount, in nearly all jurisdictions (US state sales tax, UK VAT, EU VAT, India GST, Canada HST). Tax is computed on the actual selling price, not the pre-discount list price. The handful of exceptions involve specialty taxes (some excise rules, certain luxury goods, alcohol/tobacco in specific states).

How do I find the original price from a sale price?

Divide the sale price by (1 - discount rate). For a $42 item marked "30% off": original = 42 / (1 - 0.30) = 42 / 0.70 = $60. For stacked discounts: original = sale / [(1 - d1) * (1 - d2) * ...].

What is "buy one get one 50% off" as a percent discount?

Mathematically: you pay full price for one item plus half for the second, so for 2 items you pay 1.5x the unit price. That's 1.5 / 2 = 75% of the regular total = 25% effective discount across both items. A "buy one get one free" (BOGO) deal is exactly 50% off across both items.

How is "$X off" different from "X% off"?

A flat dollar discount is a fixed amount regardless of price. A percentage discount scales with the price. $10 off a $50 item = 20% off; $10 off a $100 item = 10% off. Retailers prefer flat-dollar coupons on expensive items (smaller percentage hit) and percentage off on cheap items (smaller dollar hit).

Is a bigger discount always a better deal?

No. A 70% off "designer" handbag whose pre-discount price was set artificially high may be more expensive than a 20% off competitor whose pre-discount price was realistic. Always compare final out-the-door prices (including tax and shipping) for equivalent items, not advertised discount percentages.

Last reviewed:

Sources & references

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