Most whole hams you purchase at the grocery store, including smoked, spiral cut and whole, unsliced hams, are precooked and only require reheating before serving. Read the ham's label to be sure, however. Precooked ham can actually be eaten cold, but you might choose to reheat it, particularly if you want to add a sugary glaze.
Preheat the oven to 325 degrees Fahrenheit. Place the ham in a roasting pan.
Add a glaze to the ham before baking, if desired. You might pack the ham with brown sugar and stick pineapples to the sides with toothpicks. To make Filipino-style ham, simmer a can of pineapple juice with brown sugar to create a hot glaze, and pour the glaze over the ham. Cherry glaze is also commonly used for hams. Check the package carefully because your ham might come with a packet of glaze.
Cover the ham with aluminum foil sealed tight around the pan's edges to help lock in moisture. Aluminum foil is especially important for sliced hams because reheating tends to dry out the meat.
Bake the ham for roughly 10 minutes per pound, or until it reaches a minimum internal temperature of 140 degrees Fahrenheit. Heat it to 165 F if you're reheating a leftover ham rather than one straight out of its packaging. Insert a meat thermometer in the thickest part of the ham to get an accurate reading.
When presentation is important, it makes sense to bake a whole ham to use as a centerpiece for the table. If you have a spiral cut ham and will only eat a few slices at a time, however, it is more practical to remove a few slices at a time and heat them in the microwave.