The rule is twenty minutes per 450g, plus twenty minutes on top. It's the same rule cooks have used for generations (it's 20 minutes a pound in old money), and it works for smoked and unsmoked joints, with or without the bone.
Boiling times by weight
| Weight | Boil for |
|---|---|
| 500g | 45 min |
| 750g | 55 min |
| 1kg | 1 hr 5 min |
| 1.25kg | 1 hr 20 min |
| 1.5kg | 1 hr 30 min |
| 2kg | 1 hr 50 min |
| 2.5kg | 2 hr 15 min |
| 3kg | 2 hr 35 min |
| 3.5kg | 3 hr |
| 4kg | 3 hr 20 min |
| 5kg | 4 hr 5 min |
These are simmering times. If you're glazing afterwards, add 20 minutes in the oven at 200°C (180°C fan, gas 6), then rest the joint for 15 minutes.
"Boil" really means simmer
Every recipe says boil, and nobody means it. Bring the water to the boil, then turn it right down so it just trembles, with a few lazy bubbles. A hard boil makes the outside tough before the middle is done.
What to put in the water
Plain water works fine. An onion, a carrot, a couple of bay leaves and a few peppercorns make the gammon taste better and give you a stock worth keeping. For something sweeter, swap half the water for cola, cider or ginger beer. There's a gammon in cola recipe if you want to try it.
Is it done?
A thermometer is the only sure way. Push it into the thickest part, away from any bone, and look for 70°C, held for two minutes. That's the Food Standards Agency's guidance for pork. Gammon stays pink when it's cooked because of the curing salts, so colour won't tell you anything.
For a weight that isn't in the table, or for a different method, use the calculator above.
Straight answers
How long do you boil a 1kg gammon joint?
About 1 hour 5 minutes at a gentle simmer.
How long do you boil a 2kg gammon joint?
About 1 hour 50 minutes.
Do you start gammon in cold or boiling water?
Cold. Bringing it up to the boil slowly cooks it more evenly and draws out a little salt. Skim off any froth once it boils, then turn it down to a simmer.
Can you boil gammon too long?
Yes. It goes stringy and dry, and it starts to fall apart when you slice it. Stick to the timings and check it with a thermometer towards the end.
Do you boil gammon with the lid on or off?
Half on. A lid left slightly ajar keeps the water at a steady simmer without it boiling over or reducing too much. Top it up with boiling water if the joint starts to poke out.
Does boiled gammon need to go in the oven?
No. It's fully cooked once it reaches 70°C in the middle. The oven is only there to glaze it, which is worth doing but optional.
Updated 10 November 2026