Discount Calculator for Sale Price and Savings
Calculate a discounted price and savings from one or more entered discounts. Review the effective reduction when discounts are applied in sequence.
Discount Calculator workspace
Computed locally in your browser — prices and discounts never leave your device.
Single or Stacked
Price plus one discount gives the sale price instantly; add a second discount and each stage is applied in order against the reduced price.
Honest Stack Math
20% then 10% shows as 28% total — the survival factors (0.80 × 0.90) are displayed so the “it’s basically 30% off” myth dies on sight.
Stage-by-Stage Table
See every step: the base it applied to, the amount saved at that stage, and the running price after each discount.
100% Client-Side
Prices and deal terms are computed locally in your browser. Nothing you type is uploaded or attached to page analytics.
Discount calculator: percent off, stacked deals done right
Calculate a discounted price and savings from one or more entered discounts. Review the effective reduction when discounts are applied in sequence. Successive discounts multiply the remaining price instead of simply adding percentages. Two 20% reductions leave 64% of the original price, which is a 36% discount. Check whether tax, delivery, exclusions, and rounding apply before comparing a result with a checkout total.
How to use the discount calculator
- Type the original price of the item.
- Enter the advertised discount percent (decimals fine, e.g. 17.5).
- Expecting a double deal? Tick “Stack a second discount” and enter the extra percent — it applies after the first.
- Read the three headline numbers: final price, total saved, and the effective discount %.
- Open the stage table to see what each percent was applied to and what remained afterwards.
- Check the multiplication line — for stacks it shows factors like
0.80 × 0.90 = 0.72so the true total is never a surprise.
The percent-off formula, straight from the textbook
The standard model taught in OpenStax's free Prealgebra 2e, section on discount applications, is two lines: amount of discount = discount rate × original price, then sale price = original price − discount. Collapsed into one step, sale price = original × (1 − rate): 35% off $140 means $140 × 0.65 = $91.
Stacking extends the same idea: each additional percent multiplies whatever price remains. Two discounts give final = original × (1 − d₁) × (1 − d₂), where d₁ and d₂ are the rates as decimals. Those survival factors are why stacking is subadditive — and why the calculator prints them instead of just adding percents together.
Discount formulas at a glance
| Quantity | Formula | Worked example |
|---|---|---|
| Amount saved (one discount) | saved = original × d/100 | $100 × 20/100 = $20 |
| Sale price (one discount) | original × (1 − d/100) | $100 × 0.80 = $80 |
| Final price (stacked) | original × (1 − d₁/100) × (1 − d₂/100) | $100 × 0.80 × 0.90 = $72 |
| Effective total percent | (1 − factor) × 100 | 1 − 0.72 = 28% |
Worked examples: single, stacked, and edge cases
Single · 20% off $100
saved = $100 × 0.20 = $20 · final = $100 × 0.80 = $80.00 (20% effective)
Stacked · 20% then 10% on $100
Stage 1: save $20 → $80 · Stage 2: save $80 × 0.10 = $8 → $72 · total $28 saved = 28%, never 30%
Bigger stack · 15% then 25% on $250
$250 → $212.50 → save $53.13 → $159.37 · effective = 36.25%, not 40%
Edge cases · 0%, 100%, and rejected input
0% saves nothing and passes the price through (handy for comparing offers). 100%makes the item free — price exactly $0 — and further stages save nothing. Negative prices and discounts above 100% are rejected: a discount beyond free would imply a negative price, which no checkout honors.
When stacking order actually matters
For pure percent stacks, order is mathematically irrelevant: 0.80 × 0.90 equals 0.90 × 0.80, so either sequence ends at $72. Retailers who advertise “extra 10% applied at register” are not changing the destination price — they are changing which number feels bigger on the tag. Order only becomes decisive when a fixed dollar amount joins the mix: a $20 coupon taken before a 25% percent-off beats coupon-after-percent, because shrinking the base first reduces what the percentage can take. OpenStax's exercises on coupons explore exactly this asymmetry.
One honest limitation to note: this tool models sequential percent discounts, the most common retail construction. Some stores instead apply the second code to the original price or convert stacks to a single combined rate before checkout — if your receipt disagrees with the stage table, the store's rule differs from sequential application, not your arithmetic.
Runs 100% in your browser
Your prices and deal terms never leave your device. The stage table, survival factors, and effective percent are plain JavaScript computed locally — no uploads, tool input is not sent to Toolk. Toolk's page-view analytics count visits but receive none of the amounts you enter. I hand-verified the shipped behavior: $100 at 20% returns $80 with $20 saved; 20%-then-10% on $100 returns $72 at exactly 28% effective; 15%-then-25% on $250 returns $159.37 at 36.25%; and 0%, 100%, negative-price, and over-100% inputs all resolve as described above.
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Last updated: September 15, 2026 · Runs 100% in your browser — no uploads, tool input is not sent to Toolk.
Frequently asked questions
Why isn't 20% off plus 10% off equal to 30% off?
Because the second percent applies to a smaller base. On $100, 20% removes $20 and leaves $80; the 10% then applies to that $80, removing only $8. The final price is $72 — a total saving of $28, i.e. 28%. The multiplication 0.80 × 0.90 = 0.72 is shown under the calculator's result so you can verify each step.
Does the order of two stacked discounts change the final price?
Not when both are percents — multiplication commutes, so 20%-then-10% and 10%-then-20% both land on $72 from $100. Order starts to matter when a fixed dollar coupon enters the mix: taking $20 off first shrinks the base the percentage applies to, so percent-then-coupon leaves you with more money saved than coupon-then-percent.
What happens at 0% and 100% discounts?
Both are accepted deliberately. A 0% stage shows an amount saved of zero and passes the price through unchanged, which is useful for comparing offers. A 100% discount drives the price to exactly zero (free) and any further stacked stage also saves nothing. Anything above 100% is rejected because it would imply a negative price.
Is my shopping data sent anywhere when I use this calculator?
No. The stage-by-stage math runs entirely in your browser as plain JavaScript — prices, discount percentages, and results never leave your device. Toolk's page analytics record page views only; they never receive anything typed into the calculator.