Discount calculator: the price after the discount, and what it does to your profit.
A 10% discount on an item with a 30% margin does not cut profit by 10% but by a third, and to earn the same money you must sell half as much again. That is the arithmetic rarely done before a sale. Enter price, cost and discount and see the effect in numbers; on the other side, turn "buy N, get M" into the percentage the books see. Dashing applies promotions at the till and computes the real margin on the income statement, not the nominal one.
A percentage off
- Price after discount
- 9,000
- Saves 1,000
- Profit per unit: before → after
- 3,000 → 2,000
- Margin: before → after
- 30.0% → 22.2%
- To earn the same, sell
- +50.0%
- more units
A 10.0% discount on a 30.0% margin cuts the profit per unit by 33.3%. To earn the same money you need to sell 1.50 units for every unit you sold before.
"Buy N, get M free"
- Equals a discount of
- 33.3%
- Margin on the whole deal
- -5.0%
The customer reads "one free"; the books read a discount across three units. The number above is what the books see — at the price and cost you entered on the left.
How to calculate a discount
Sale price = original price × (1 − discount ÷ 100), and the saving is the difference. 25% off 80 is 80 × 0.75 = 60, a saving of 20. To find the percentage from two prices: (1 − new price ÷ old price) × 100, so 45 instead of 60 is 25% off. Two discounts in a row do not simply add up: 20% and then 10% off comes to 28% in total.
The rule of thirds
The share of profit that goes = discount ÷ margin. A 10% discount on a 30% margin takes a third of the profit; on a 20% margin, half; on a 10% margin, all of it. That is why high-margin items get discounted and devices do not.
When a discount is worth it
When you believe volume will rise by at least the percentage shown here — or when the goal is not profit: clearing an item before it expires, drawing a customer who buys other things, matching an offer on the same street. Name the goal before you compute.
Common questions
How much more must I sell to make up for a discount?
Divide the old profit per unit by the new one. An item priced at 10,000 that costs 7,000 makes 3,000; at 10% off it makes 2,000, so you must sell 1.5 units for every unit you sold before, 50% more.
What does "impossible" mean?
That the discount is at least as large as the margin: the new price is at or below cost, and no volume makes it back. It is acceptable only when the goal is to clear stock that would otherwise be lost.
Does this apply to a whole-invoice discount?
Yes, with the basket's average margin. A 5% discount on a basket with a 20% margin takes a quarter of its profit.
How do I run the offer at the till?
In Dashing, from Pricing & offers: a promo code, a percentage on chosen items, or a quantity deal — applied at the till automatically and measured in the reports.