How do I calculate how many more units I need to sell with a discount?

Divide your margin per unit at full price by your margin per unit after the discount, and multiply by the units you sell now. With a price of 40, a cost of 22 and 20% off, the margin falls from 18 to 10, so you need 18 ÷ 10 = 1.8 times the units: 80% more, just to make the same gross profit.

Why does a small discount need so many extra sales?

Because the whole discount comes out of your margin, not out of the price. 20% off a price of 40 is 8, and 8 is almost half of an 18 margin. The thinner your margin, the more volume each point of discount has to buy back, and once the discount is as large as your margin every sale loses money.

Is a discount ever worth it?

It can be: to clear stock, to win back customers who stopped buying, or when a first order leads to repeat purchases. This calculator only looks at the gross profit on the discounted sales and leaves those effects out. It also ignores the customers who would have bought at full price anyway, which is the main reason to offer a discount to a chosen group rather than to everyone.

Where does my data go?

Nowhere. The arithmetic runs in your browser. Nothing you type is sent to us, stored, or needed to see the result, and there is no signup.

Free tool — no signup

How much more do you have to sell to pay for a discount?

A discount feels like it pays for itself in extra orders. Put in your price, your cost and the discount you are thinking about, and see how many more units you would have to sell just to make the same gross profit you make today.

Product price What the customer pays at full price.

Unit cost What one unit costs you: product, packaging, fees.

Units you sell now Per month, at full price.

Discount Percent off the price.

Currency Only changes how the figures are written.

With 20% off you need to sell 360 units a month instead of 200 (80% more) just to keep the same gross profit.

Margin per unit now

$18.00

price − cost

Margin per unit with the discount

$10.00

discounted price − cost

Gross profit now

$3,600

per month

Units needed with the discount

360

per month, for the same gross profit

More units you have to sell

+80%

just to stand still

The same product at other discounts

Discount	Units needed	Extra units
10% off	258	+29%
15% off	300	+50%
20% off	360	+80%
25% off	450	+125%
30% off	600	+200%

Discount

Units needed

Extra units

10% off

258

+29%

15% off

300

+50%

20% off

360

+80%

25% off

450

+125%

30% off

600

+200%

Gross profit here is price minus unit cost, before ads, shipping you pay for and fixed costs. It answers one question: how much more volume the discount has to buy back.

How it is calculated

There is no model here and nothing is hidden:

Margin per unit now = price − unit cost.
Margin per unit with the discount = price × (1 − discount) − unit cost.
Gross profit now = margin per unit now × units you sell now.
Units needed = gross profit now ÷ margin per unit with the discount, rounded up to a whole unit.
More units you have to sell = margin now ÷ margin with the discount − 1.

When the discount is as big as your margin as a share of the price, the margin with the discount is zero or less, and no volume can make up for it: every extra sale loses more.

What it assumes, stated plainly

That every unit is sold at the discount. If only some customers use the code, the extra volume you need is smaller.
That your unit cost stays the same as you sell more. Buying in larger quantities may lower it; paying for faster restocking may raise it.
That the customers buying with the discount would not have bought anyway. Some would have, and each of them is margin you gave away for nothing.
That nothing happens after the first order. A discount that brings in a customer who comes back has a value this page does not count.

Discount a segment, not everyone

The cheapest discount is the one only the right people see. With Super Agent campaigns you send an offer on WhatsApp to a segment of your customers — for example, people who bought before but not in the last few months — instead of cutting the price for everyone, and each campaign reports the orders it produced.

Start free

Free plan, no credit card, live the same day.

Questions

How do I calculate how many more units I need to sell with a discount?: Divide your margin per unit at full price by your margin per unit after the discount, and multiply by the units you sell now. With a price of 40, a cost of 22 and 20% off, the margin falls from 18 to 10, so you need 18 ÷ 10 = 1.8 times the units: 80% more, just to make the same gross profit.
Why does a small discount need so many extra sales?: Because the whole discount comes out of your margin, not out of the price. 20% off a price of 40 is 8, and 8 is almost half of an 18 margin. The thinner your margin, the more volume each point of discount has to buy back, and once the discount is as large as your margin every sale loses money.
Is a discount ever worth it?: It can be: to clear stock, to win back customers who stopped buying, or when a first order leads to repeat purchases. This calculator only looks at the gross profit on the discounted sales and leaves those effects out. It also ignores the customers who would have bought at full price anyway, which is the main reason to offer a discount to a chosen group rather than to everyone.
Where does my data go?: Nowhere. The arithmetic runs in your browser. Nothing you type is sent to us, stored, or needed to see the result, and there is no signup.

More free tools

Missed-reply calculator — What the calls and messages nobody answers cost you each month.
Abandoned cart calculator — How much money is sitting in abandoned checkouts, and how much a reminder could bring back.
WhatsApp link generator — A wa.me link with a prefilled message, a button for your site and a UTM-tagged URL.
See all free tools