Turkey Size Calculator: What Size Turkey Do I Need?

Buy the turkey too small and someone goes without; buy it too big and it may not fit the oven or the fridge. The usual rule of thumb is about 500g of whole, bone-in bird per person, because a good share of the weight is bone and carcass, while a crown or a boneless roll needs much less. Enter who is eating and how much you want left over for Boxing Day, and this gives you the weight to order, a version for each cut, and the date to move a frozen bird into the fridge.

How the turkey size is worked out

The calculator counts adult portions (children under 12 count as half), then multiplies by a raw weight per portion for the cut you are buying, an appetite factor and a leftovers factor. It then rounds up to the next half kilo, because turkeys are sold by size bands and running short at the table is worse than a few extra sandwiches.

• Whole turkey: about 500g per adult. Bone, skin and the carcass make up a large share of a whole bird, so the carved meat is much less than the weight on the label.
• Crown: about 300g per adult. A crown is the breast still on the rib bone, with the legs and wings removed, so less of it is waste.
• Boneless roll or joint: about 225g per adult, since almost everything you buy ends up on a plate.

Leftovers add 30% for sandwiches and a curry, or 60% if you want a second full meal. If your family eats mainly the breast, a crown gives you more of what they want for the same money and takes less oven room.

Will it fit in your oven?

Weight is only half the question for a range cooker. Measure the inside of the oven you plan to use, then measure your largest roasting tin, and leave a few centimetres of clear space around the tin so hot air can circulate. A dual-cavity range cooker usually has one wider main oven; check which side is larger before you order. On an Aga, check the height as well as the width: a tall bird in a deep tin may only fit on the lowest runners. If the numbers say you need a bird that is too big for your oven, buy a crown plus a separate leg joint instead.

Thawing a frozen turkey safely

The safest way to defrost a turkey is slowly, in the fridge. The calculator plans on 12 hours per kilo, the top of the usual 10 to 12 hour range, and times it to finish by 8am on the day you cook. That is why a big bird needs to come out of the freezer days ahead, not the night before. Clear a fridge shelf first; a large turkey on a tray takes up most of one. For other joints and other thawing methods, use our meat defrosting time calculator.

Next: cooking times and the full roast

Once you know the weight, get the oven temperature, cooking time and resting time from the roasting time calculator, which covers both conventional range cookers and the Aga method. Then plug the same weight into the roast dinner timing calculator to get a timeline for the turkey, roast potatoes, pigs in blankets and veg, so it all lands on the table together.