A bottle imported from the UK is labelled in fluid ounces: can I compare it with a bottle sold in millilitres?
Yes, but enter it in millilitres, not fluid ounces. The tool's fluid ounce is the US one (about 29.57 ml), while the UK fluid ounce is slightly smaller, so entering a UK label as US fluid ounces overstates the bottle's contents and makes it look cheaper than it is. UK packs usually print the millilitre figure too, so use that.
The two fluid ounces
There are two definitions: the US fluid ounce, 29.5735295625 ml, and the UK imperial one, 28.4130625 ml. The tool supports only the US one and says so in the unit name: fl oz (US fluid ounce). The difference is about 4% per ounce, enough to change the outcome of a close comparison.
An example in numbers
A UK shampoo at 25 labelled 16 fl oz / 454 ml, against a local 500 ml bottle at 30:
- Entered correctly, 454 ml against 500 ml: the UK bottle is 55.0661 per litre and the local one 60 per litre, so the local bottle is 8.96% more expensive.
- Entered wrongly, as 16 US fluid ounces: the tool treats that as about 473 ml, the UK bottle drops to 52.8344 per litre, and the local one looks 13.56% more expensive.
Here the UK bottle stays cheaper either way, but the mistake inflates the gap from about 9% to about 14%. With prices closer together, the same slip can flip the result and have you buy the dearer bottle.
Entering it correctly
- Find the millilitre figure on the pack. UK products usually print it next to, or instead of, the fluid ounces.
- In the Unit-price comparison tool, enter both bottles with the ml (millilitre) unit.
- Choose per litre or per 100 ml under Show cost, and read the result.
- Use the tool's fl oz unit only for US products labelled US fl oz.
How do you know the label is British?
From the country of origin on the pack, or from an ml figure printed alongside the ounces. If you see only fl oz with no country and no ml, ask the seller for the millilitre volume rather than guessing. The same applies to gallons: the tool's gallon is the US one, and the imperial gallon is noticeably larger.
If the imported bottle has an in-store discount, work out its price after the discount with the Discount calculator before comparing.
Common questions
Why does the tool not support UK fluid ounces?
It uses US measures only to avoid mix-ups, and says so in the unit name and its limitations.
Is the weight ounce different too?
The tool's weight ounce (oz) is 28.349523125 g, a unit of mass, not volume.
The pack shows ٤٥٤ in Eastern Arabic digits. Do I convert it?
The fields accept it as it is. If you want to copy it into a file, convert it with the Arabic/Persian/Western digit converter.