Percentage & Discount Calculator
Work out sale prices, discount rates, ratios, percent change and proportions as you type, or work back to the original price or cost, with the formula shown.
What is the price after the discount?
Enter two values to calculate instantly.
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Percentage & Discount Calculator: complete guide
Walk through the steps and examples, or jump straight to the topic you need.
At a glance
- Calculation modes
- Nine calculations: Discount, B% of A, A is what % of B, Discount rate, Change, Apply change, Original value, Cost from margin and Proportion.
- Input
- Enter numbers of 0 or more; decimals are allowed. The discount rate is 0 to 100% and the margin rate must be below 100%. For Apply change and Original value, put a − in front for a decrease; the value must be greater than −100%.
- When it calculates
- It calculates immediately once the required inputs (three values for a proportion) are valid. If an input is empty, no result is produced.
- Display
- Shows the result together with the formula, with up to six decimal places.
- Range
- Inputs and results must stay within the range of numbers that can be handled safely. Division where the whole or the old value is 0 is not supported.
How to use Percentage & Discount Calculator
Choose the calculation by the value you want
To find the amount to pay at a known discount, choose Discount; to find what percent off a list price and sale price imply, choose Discount rate. To find one unknown value from a ratio, use Proportion. Use Ratio for the share a part takes of a whole, and Change for how much something changed from before. The input labels change when you switch modes, so check them again.
Enter both values in the same unit
Compare amounts with amounts or counts with counts. For a ratio, the order of part and whole matters; for a percent change, the order of old and new matters. Do not add symbols such as currency or %; enter just the number that fits the input label.
Read the result together with the formula
A discount result is the amount after the discount, and the discount amount is shown separately. A negative percent change means a decrease. If a ratio is above 100%, check whether the value you entered as the part is larger than the whole.
Copy the value you need
You can copy the result into a quote or a document you are working on. Displayed values are rounded, so in multi-step calculations be careful not to round intermediate results repeatedly.
What it’s good for
The price after a discount, and B% of A
Take 20% off KRW 10,000 and the discount is KRW 2,000, leaving KRW 8,000. Discount finds what remains, while B% of A finds the amount that corresponds to a given share of a whole. Use them when you already know the percentage. If you only know the list price and the sale price, choose Discount rate. For an item that was KRW 50,000 and is now KRW 35,000, (50,000 − 35,000) ÷ 50,000 × 100 = 30% off.
The difference between a ratio and a percent change
A ratio is part ÷ whole × 100. 20 out of 100 is 20%. A percent change is (new value − old value) ÷ old value × 100, so going from 100 to 120 is a 20% increase. Going from 20% to 30% is a rise of 10 percentage points, but the relative change is 50%.
Finding an unknown value with a proportion
In a : b = c : x, x is b × c ÷ a. If 3 servings take 5 spoons of sugar, 12 servings take 5 × 12 ÷ 3 = 20 spoons. You can use it as it is for map scales, scaling up recipes and conversion ratios.
Worked examples
20% off KRW 10,000
Discount · Original price 10000 · Discount rate 20Price after discount 8,000
Discount amount 2,000An increase from 80 to 100
Change · Old value 80 · New value 10025% increase
Difference +20Formula and meaning for each mode
Swipe the table sideways to see the rest.
| Mode | Formula | What it finds |
|---|---|---|
| Discount | Original value × (1 − discount rate ÷ 100) | The amount left after the discount |
| B% of A | Whole × percent ÷ 100 | The amount that corresponds to a given share |
| A is what % of B | Part ÷ whole × 100 | The share the part takes of the whole |
| Change | (New − old) ÷ old × 100 | Relative change measured against the old value |
| Discount rate | (List price − sale price) ÷ list price × 100 | The share taken off the list price |
| Proportion | x = b × c ÷ a | The unknown value in a : b = c : x |
When the result isn’t what you expected
I entered 0 and nothing is calculated
The whole in a ratio and the old value in a percent change are divisors, so they cannot be 0. Check the real base value and correct it. A discount amount or a part value of 0 is allowed.
It went up 10% then down 10%, but it is not the original value
The second change is calculated against the changed value. 110, which is 100 plus 10%, drops to 99 after a 10% decrease. It is the result of applying the same percent to different bases.
The result differs from the percentage points
The rise from 20% to 30% is 10 percentage points. The percent change is calculated against 20, so it is 50%. Check whether you want the simple difference between the two percentages or the relative change.
Key terms
- Percent
- A ratio expressed with the whole taken as 100.
- Percentage point
- The simple difference between two percent values.
- Base value
- The number that serves as the denominator when comparing a ratio or a change.
Percentage & Discount Calculator FAQ
Can it calculate ratios above 100%?
The B% of A and A is what % of B calculations support values above 100%. In Discount mode, the discount rate is limited to 0 to 100%.
Can I calculate a percent change if the base value is 0?
If the old value is 0, there is no base to divide by, so the percent change cannot be calculated. In ratio calculations too, an error is shown if the whole is 0.
How many decimal places are shown?
Results are shown to six decimal places. The rounded result on screen can differ slightly from the internal calculated value.
Can I enter a list price and sale price to find the discount rate?
Choose Discount rate and enter the list price and the price after the discount; it shows the percent off and the discount amount. If the sale price is higher than the list price, the result is negative, meaning a markup. Discount mode works the other way around: it finds the price after a discount from a rate you already know.
Can I apply several discounts?
It calculates one step at a time. For successive discounts, use the amount after the first discount as the original value of the next calculation. Simply adding the discount rates together can give a different result.