This can vary.
In the UK ounces of weed sometimes tend to be slightly smaller than the official converted weight in grammes. Here’s why:
A kilo of weed or hash is often made up of four ‘nine bars’. A nine bar weighs 250 grammes, or quarter of a kilo. Or just under nine ounces.
The nine bar is divided into nine. This means that 250 grammes is divided by nine – which makes 27.7 grammes. This is just under how much an ounce converted directly to grammes weighs.
The official weight of an ounce is 28.3495 grammes – so if you get that you are doing well.
It all depends on the dealer.