THE SHORT ANSWER
Buy 3, get 1 free is equivalent to 25% off
You receive four items and one is free. In other words, one-fourth of the total is free.
Turn “free” into a discount you can compare
Free-item promotions sound different from a regular percent-off sale. To compare them, count every item you receive, then find what fraction of that total is free.
If each item costs $5, you pay $15 for three and receive a fourth item free. The same four items would normally cost $20, so you save $5.
Check the total and price per item
Scroll sideways to see the full table.
| Detail | Regular price | Buy 3, get 1 free |
|---|---|---|
| Items received | 4 | 4 |
| Total paid | $20.00 | $15.00 |
| Price per item | $5.00 | $3.75 |
| Effective discount | 0% | 25% |
The formula for any buy-X-get-Y-free offer
Effective discountFree items ÷ (paid items + free items) × 100
Scroll sideways to see the full table.
| Promotion | Effective discount |
|---|---|
| Buy 1, get 1 free | 50% |
| Buy 2, get 1 free | About 33.33% |
| Buy 3, get 1 free | 25% |
| Buy 4, get 1 free | 20% |
Details to check before you buy
- Which item is free? In mixed-price promotions, the least expensive eligible item is often the free one.
- Which combinations qualify? Sizes, flavors, and brands may be restricted.
- Do you need the full quantity? A 25% effective discount does not help if part of the purchase goes unused.