Work out the final price and savings on a discount, or calculate percentages and proportions — all in one place.
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This tool's discount calculator uses the "out of 10" scale common across East Asia: a level of 10 means no discount at all, and a level of X means you pay X/10 of the original price (i.e. X × 10%). The underlying formula is simple: final price = original price × level ÷ 10. For example, a level of 8 means original price × 8 ÷ 10 = 80% of the price. This is the inverse of the Western "XX% off" convention — the level tells you what you pay, while "% off" tells you what you save. The conversion is: level = 10 − (percent off ÷ 10). So "level 8" equals "20% off," and "level 6.5" equals "35% off."
The most common error is seeing "level 6" and assuming it means 6% off — it actually means you pay 60% and save 40%. A smaller level number means a bigger discount, which runs opposite to normal percentage intuition. A second common mistake is assuming two stacked discounts simply add together — e.g. "20% off, then another 20% off" is often mistaken for "40% off total." The correct method multiplies the remaining fractions in sequence: original price × 0.8 × 0.8 = 0.64, meaning you actually pay 64% (a combined 36% off, not 40%) — a smaller saving than the naive addition suggests. This calculator only computes a single discount at a time; to work out stacked discounts, take the result of the first calculation and re-enter it as the "original price" for a second pass.
Applying the formula: final price = 2,580 × 7.5 ÷ 10 = 2,580 × 0.75 = 1,935. Amount saved = 2,580 − 1,935 = 645. You can cross-check this with the percentage calculator: enter A = 645 and B = 2,580 in the "A as a percentage of B" fields, and it returns 25% — matching the expected relationship (10 − 7.5 = 2.5, and 2.5 × 10% = 25%). When both calculators agree like this, it's a good way to sanity-check your own math.
The percentage calculator handles two distinct, commonly confused questions. The first: "given a whole and a percentage, what's the value?" — e.g. "I spend 45,000 and get 5% cash back — how much is that?" Enter 45,000 in the Number field and 5 in the Percent field to get 2,250. The second is the inverse: "given a part and a whole, what percentage is the part?" — e.g. "9 out of 40 students in a class wear glasses — what percentage is that?" Enter A = 9 and B = 40 to get 22.5%. These two directions are mathematical inverses of each other, which is exactly why they're split into two separate field groups — so you can plug numbers straight in without mentally flipping the direction yourself.
Not directly — it only computes one discount at a time. For stacked discounts (e.g. a sale price further reduced by a coupon), do it in two steps: calculate the first discount's final price, then re-enter that amount as the new "Original Price" for a second calculation. Stacked discounts multiply the remaining fractions together — they don't simply add as percentages.
The field is intended for the 0–10 range (above 10 would mean "more expensive than the original price," which isn't a real discount), but the browser doesn't hard-block out-of-range numbers. Entering a value above 10 will produce a final price higher than the original; a negative value produces a negative amount. Both are mathematically accurate outputs of the formula, but neither represents a real-world discount — stick to values between 0 and 10 for meaningful results.
The tool specifically guards against this: dividing by zero is mathematically undefined, so when B is 0, the result is simply shown as 0% instead of an error or a broken calculation — this fallback is intentional.
A few possibilities: the store's promotion might be a flat cash amount off, a "buy one get one at X% off" deal, or another non-proportional rule rather than a straight percentage discount; the "original price" on the receipt might already reflect an earlier markdown; and some retailers round to the nearest whole currency unit at checkout, while this tool shows results to two decimal places. Treat the register total as authoritative — this calculator is meant for simple "original price × discount level" estimates.
No. Both the discount and percentage calculations run entirely in your browser using JavaScript — there's no fetch call or network request sending your data out. Reload the page and whatever you typed is gone; nothing is stored or logged anywhere.