THE SHORT ANSWER
Buy 3, get 1 free is equivalent to 25% off
For four eligible items with the same regular price, you pay for three and receive one free: a 25% discount on that set. Different prices or extra items outside the set change the overall percentage.
Does it mean three items or four?
“Buy 3, get 1 free” means paying for three and taking home four. It is different from getting one free out of three total items. Check the offer's wording, then count every item you receive when working out the discount.
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
This formula assumes one complete set of equally priced items. Count the items you pay for separately from the free ones.
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% |
Five items do not all get 25% off
Suppose each item costs $5, the offer repeats for each complete group of four, and any leftover items cost full price. These are hypothetical terms; check whether your offer limits the number of free items.
Scroll sideways to see the full table.
| Items received | Free items | Payment | Discount on the whole purchase |
|---|---|---|---|
| 3 | 0 | $15 | 0% |
| 4 | 1 | $15 | 25% |
| 5 | 1 | $20 | 20% |
| 8 | 2 | $30 | 25% |
For five items, the $5 saving is divided by the $25 regular total, so the whole purchase is 20% off. A separate 25%-off sale on the same five items would cost $18.75, saving $1.25 more.
Enter 5 in the calculator's “Total items to take home” field to check the $20 payment and 20% discount. This count includes the free item; the calculator does not add it on top of your total.
If the cheapest item is free, use prices instead of counts
In a hypothetical eligible set priced at $8, $6, $5, and $3, suppose the offer makes the $3 item free. The regular total is $22 and the payment is $19. The discount is $3 ÷ $22 × 100, or about 13.64%, even though one of four items is free.
For mixed prices, divide the actual value of the free items by the regular total of all eligible items. The count-based calculator assumes equal prices and cannot apply a store's mixed-price rules for you.
Compare the amount you need, too
If you need only two $5 items, buying them normally costs $10; completing a buy-3-get-1-free set costs $15. You save money compared with buying four at full price, but spend $5 more than you need to. If you need three, taking the free fourth leaves the same $15 payment. Whether you can use it before it expires is a separate decision.
These examples exclude tax and shipping and assume no other discounts. Check the final cart when an offer changes which items qualify.
Details to check before you buy
- Which item is free? Check whether the offer makes the least expensive eligible item free.
- Which combinations qualify? Sizes, flavors, and brands may be restricted.
- Can you use the full quantity? A lower price per item does not necessarily mean a lower cost for what you will use.