How this calculator works
Ham comes in three states and they are cooked very differently. A smoked ham labelled cook before eating is raw in the middle and must reach a safe internal temperature. A fully cooked ham only needs to be reheated, which takes less time and a lower internal temperature. A fresh ham is uncured pork leg and behaves like a pork roast. Within each type, the cut changes the rate: a bone in ham heats more slowly per kilogram than a boneless one of the same weight because the bone takes up part of the mass, and a half ham cooks more slowly per kilogram than a whole one because it has more exposed surface for its weight. The rates on this page are the published USDA roasting times at 325 F (163 C). A ham should be cooked to temperature, so treat the time as the moment to insert a thermometer and start checking.
Formula
minutes per kilogram = minutes per pound x 2.20462. cooking time = minutes per kilogram x weight in kilograms. The rates at 325 F are 18 to 20 minutes per pound for a whole cook-before-eating ham, 22 to 25 for a half, and 35 to 40 for a shank or butt portion. Fully cooked hams use 15 to 18, 18 to 24, 25 to 30 or 10 to 18 minutes per pound depending on the cut, and fresh hams use 22 to 26 for a whole leg and 35 to 40 for a half leg.
Worked example
A 4 kg cook-before-eating whole ham, bone in, has a rate of 18 x 2.20462 = 39.7 to 20 x 2.20462 = 44.1 minutes per kilogram. The cooking time is 159 to 176 minutes, or about 2 hours 39 minutes to 2 hours 56 minutes at 325 F. A 3 kg fully cooked half ham uses 18 to 24 minutes per pound, which is 39.7 to 52.9 minutes per kilogram and 119 to 159 minutes in total. Both need a thermometer check before the end of the range.
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Frequently asked questions
What internal temperature should ham reach?
Health Canada lists 71 C (160 F) for pork cuts, including ham. The USDA chart for cook-before-eating ham uses 145 F (63 C) followed by a three minute rest, and 140 F (60 C) for reheating a fully cooked ham. Use 71 C for a Canadian kitchen unless the packaging gives its own tested instruction.
Why does a half ham take longer per kilogram?
A half ham has more exposed surface and less mass for its size, so it loses heat to the oven more quickly and its shape is less even. The published rates reflect that, which is why a half ham can need 35 to 40 minutes per kilogram while a whole leg needs about half that.
Should I cover the ham?
Covering slows browning and keeps the outside moist, and many recipes cover for part of the time and uncover near the end to glaze. Covering also slows the rise in internal temperature, so start checking early if you change the method.
Can I cook a spiral sliced ham for as long as a whole ham?
No. Spiral sliced hams are already fully cooked and cut, so they dry out quickly. The published rate is 10 to 18 minutes per pound, and the ham only needs to be reheated to 60 C (140 F).
What about country ham?
Country ham is dry cured and very salty, and it is usually soaked and then simmered rather than roasted. Its times depend on the cure and the soaking, so it does not fit this table and is left out on purpose.