Decant vs full bottle.

Worked example

A 100 ml bottle at $150 costs $150 / 100 = $1.50 per ml. A 5 ml decant at $20 costs $20 / 5 = $4.00 per ml, a markup of 4.00 / 1.50 - 1 = 167%. If you expect to wear 30 ml, you need 30 / 5 = 6 decants = $120, which is $30 less than the bottle. The price catches up at 8 decants: 7 decants (35 ml) cost $140, but 8 decants (40 ml) cost $160, more than the $150 bottle.

How it works

Price per ml = price / size. Markup = decant price per ml / bottle price per ml - 1. Decants needed = expected ml / decant size, rounded up, and their cost = decants x decant price. Break-even decants = bottle price / decant price, rounded up. The tool compares only money; it ignores shipping, tax and resale value of an unused bottle.

What this is not. Whether a decant is authentic or how it was stored is not something a calculator can judge. A bottle you finish also gives you a full-size atomizer and box; a decant does not. If you will not finish the bottle, the decant side often wins even at a high markup, which is why the expected ml matters most.

Sources and basis: pure arithmetic on the numbers you enter; no published figure is used, and any default marked as an assumption or rule of thumb is not a published standard.

FAQ

Is it cheaper to buy a perfume decant or a full bottle?

Per ml the full bottle is cheaper whenever the decant carries a markup, which the figure above shows. In total spend, decants win when you will only use a small part of the bottle. Enter your expected ml above to see where yours falls.

How many sprays are in a 5 ml decant?

At 0.1 ml per spray, an assumption you should check on your own atomizer, a 5 ml decant gives about 50 sprays, which is roughly 12 wears at 4 sprays each. The sprays-per-bottle calculator shows how to measure your own ml per spray.

Does this work for 2 ml sample vials?

Yes. Enter 2 as the decant size and the vial price. The markup figure shows how its price per ml compares with the bottle.

When does the full bottle become the better buy?

When the number of decants you would buy costs as much as the bottle. The break-even line shows that count; with the example numbers it is 8 decants of 5 ml.