How Long to Cook Gammon & Ham
A raw gammon joint takes about 20 minutes per 450g (1 lb) plus 20 minutes extra when boiled, or 30 minutes per 450g plus 30 minutes extra when roasted at 180°C/350°F — so a 2 kg (4.4 lb) joint needs roughly 1 hour 40 minutes boiled or 2 hours 30 minutes roasted. A fully cooked ham, by contrast, only needs reheating to 140°F (60°C) internal, not full cooking. Those are two different jobs with two different clocks, and most of the confusion around "how long to cook ham" comes from not knowing which one you're actually holding.
Gammon vs Ham: What's Actually the Difference
Gammon is the raw, cured hind leg of pork — cured the same way bacon is, but sold as a whole joint. It is not safe to eat until it's fully cooked. Once cooked (by boiling, roasting, or slow-cooking), it becomes ham. That's standard UK/Commonwealth terminology, and it's also where the confusion starts: in the US, "ham" covers both the raw cut and the finished product, and most American grocery-store ham is already fully cooked at the factory — so "cooking" it at home really means reheating and glazing. If your label says "fully cooked," "spiral-cut," or "ready to eat," you're reheating. If it says "cook before eating," "fresh," or you bought a gammon joint, you're cooking from raw — the times below assume that case unless noted.
Cook Time by Weight — Boiling vs Roasting (Raw Gammon)
| Weight (lb / kg) | Boiling (mins) | Oven-Roasting at 180°C/350°F (mins) |
|---|---|---|
| 2 lb / 0.9 kg | 60 (1 hr) | 90 (1 hr 30 min) |
| 3 lb / 1.4 kg | 80 (1 hr 20 min) | 120 (2 hrs) |
| 4 lb / 1.8 kg | 100 (1 hr 40 min) | 150 (2 hrs 30 min) |
| 5 lb / 2.3 kg | 120 (2 hrs) | 180 (3 hrs) |
| 6 lb / 2.7 kg | 140 (2 hrs 20 min) | 210 (3 hrs 30 min) |
| 7 lb / 3.2 kg | 160 (2 hrs 40 min) | 240 (4 hrs) |
| 8 lb / 3.6 kg | 180 (3 hrs) | 270 (4 hrs 30 min) |
These use 20 minutes per pound plus 20 extra for boiling, and 30 minutes per pound plus 30 extra for roasting — a common UK rule of thumb. Some recipes round to 500g instead of 450g (1 lb) as the base unit, shifting the numbers by about 10%; either works, so follow your packet if it gives a figure. A popular combination method boils for half the calculated time, then finishes in a hot oven (220°C/200°C fan) with a glaze for the last 20-30 minutes — moist meat from boiling, a caramelized exterior from the oven.
Slow Cooker Method
On low, plan for roughly 1 to 1.5 hours per pound (2-3 hours per kg), submerged in water or stock with bay leaves, peppercorns, and a halved onion. This is the most forgiving method for timing, since slow cookers hold food safely once done — but it won't glaze itself. Finish with 15-20 minutes in a hot oven (220°C/425°F) after glazing, same as the boil-then-roast method above.
Two Different Temperature Targets — Don't Mix Them Up
This is the part that trips people up most, because two genuinely different products get called "ham" and searched for the same way:
| Product | What You're Doing | Target Internal Temp |
|---|---|---|
| Fully cooked ham (most US supermarket ham) | Reheating only | 140°F / 60°C |
| Fresh/raw ham (USDA, US) | Cooking from raw | 145°F / 63°C + 3 min rest |
| Raw gammon (UK guidance) | Cooking from raw | 70-75°C / 158-167°F |
The gap between the US fresh-ham figure (63°C) and the UK gammon figure (70-75°C) isn't a typo — it reflects genuinely different official guidance and curing conventions between the two countries, similar to the country-by-country differences in pork chop safe temperatures covered elsewhere on this site. If your packaging gives a number, use that one. Working from a generic recipe with no clear convention? Cook to the higher figure you're choosing between, then rest before carving.
Do You Need to Soak It First?
Usually not. Modern commercial curing is milder than it used to be, and most supermarket gammon joints are ready to cook straight from the packet. Soak for 1-2 hours, changing the water once, if the packaging specifically flags a strong or traditional cure, or up to 12-24 hours for an old-fashioned, heavily salted joint from a butcher. When in doubt, check the packet — it will usually tell you.
Glazing Without Burning It
Sugar-based glazes (honey, marmalade, brown sugar, mustard) burn quickly under direct high heat, so they go on near the end, not the start. Score the fat in a diamond pattern, brush on the glaze, and give it 20-30 minutes at 220°C/425°F — enough to caramelize without scorching. If basting more than once, use thin layers; a thick coat traps steam and can slide off instead of setting.
Why Spiral-Cut Ham Dries Out Faster
Spiral-cut ham exposes far more surface area to the oven's dry heat than a solid joint of the same weight, so it loses moisture faster throughout the whole cook. Cover loosely with foil for most of the reheating time, add a splash of stock or water to the pan, and only uncover for the final 15-20 minutes to set the glaze. Basting with the pan juices helps more here than with a whole joint, simply because there's more exposed surface to keep moist.
Resting
Rest for 15-20 minutes before carving, tented loosely with foil. This matters more for gammon/ham than for many cuts because the joint is large and dense — carving immediately pushes out juices that would otherwise redistribute, leaving drier slices.
Frequently Asked Questions
Is gammon the same as ham?
No. Gammon is the raw, cured hind leg of pork — it still needs full cooking before eating. Ham is the same cut once cooked (or, in the US, is usually sold already fully cooked and only needs reheating). All ham starts as gammon; it just isn't called ham until it's cooked.
How long do you cook gammon per kg?
Boiled: about 40 minutes per kg (20 min/lb) plus 20 minutes extra. Oven-roasted: about 60 minutes per kg (30 min/lb) plus 30 minutes extra. A 2 kg (4.4 lb) joint is roughly 1 hr 40 min boiled or 2 hr 30 min roasted. Confirm with a meat thermometer — this is a starting estimate, not a guarantee.
What temperature should cooked ham be?
Depends which kind. A fully cooked ham (most US grocery-store ham) only needs reheating to 140°F (60°C). A raw/fresh ham or gammon needs full cooking — USDA guidance for fresh ham is 145°F (63°C) plus a 3-minute rest, while many UK gammon recipes target a higher 70-75°C (158-167°F). Check your packaging; when unsure, use the higher figure.
Do you need to soak gammon before cooking?
Usually not — modern curing is milder, so most supermarket joints go straight in the pot. Soak for 1-2 hours (up to 12-24 for a heavily salted, old-fashioned cure), changing the water once, only if the packet flags a strong cure or you're worried about saltiness.
Why does spiral-cut ham dry out faster than a whole joint?
The spiral cuts expose far more surface area to dry oven heat, so moisture evaporates faster than from an intact joint of the same weight. Cover loosely with foil for most of the cook, add a little liquid to the pan, and only uncover for the last 15-20 minutes to set the glaze.