Put in the weight of your joint and choose how you're cooking it. The calculator gives you each stage separately, so you know when to turn the oven on and when to start the potatoes.
How the times are worked out
For simmering, we use the long-standing British rule of 20 minutes per 450g plus 20 minutes, rounded up to the nearest five minutes. Glazing is 20 minutes at 200°C (180°C fan, gas 6) on a joint that's already cooked through. Resting is 15 minutes for most joints, or 20 for anything over 2kg.
These are a guide rather than a guarantee. Ovens vary, pans vary, and so do joints. A meat thermometer costs less than the gammon and takes the guesswork out completely. Push it into the thickest part and look for 70°C.
Timing a dinner
Work backwards from when you want to eat. Take the total from the calculator, add 15 minutes for getting the pan up to the boil, and that's when the gammon needs to go on. For Christmas Day, there's a full countdown on the Christmas gammon page.
Straight answers
Should I weigh the gammon with or without the packaging?
Without. Use the weight printed on the label, or weigh the joint itself on kitchen scales.
Does a joint on the bone take longer?
Very slightly, because the bone slows the heat getting to the middle. Use the same timings and check it with a thermometer, pushing it in close to the bone without touching it.
My joint is a weird shape. Do the times still work?
They're a reliable guide, but a long, thin joint cooks faster than a short, fat one. Start checking the temperature about 15 minutes before the time is up.
What temperature should cooked gammon be?
70°C in the thickest part, held for two minutes. That's the Food Standards Agency's guidance for pork, and it applies to gammon too.
Updated 10 November 2026