roasting times for an unstuffed turkey: 10-12 lb (4.5-5.5 kg) 3-3 1/4 hours. 12-16 lb (5.5-7.25 kg) 3 1/4-31/2 hours. 16-20 lb (7.25-9.0 kg) 3 1/2-4 1/2 hours.