How this calculator works
A steak cooks by heat moving from the hot surface toward the centre. The distance to the centre is half the thickness, so a steak twice as thick takes much longer than twice the time in a simple model, but real cooking evens this out: the surface also browns faster on a thin steak and the centre of a thick one needs more rest. Published charts show the total time rising with thickness more slowly than a straight doubling, which is why this page scales the 1 inch time by the square root of the thickness in inches. Method matters too: a hot grill or pan drives heat in faster than an oven, so a sear then roast takes about a fifth longer. The only reliable test is a thermometer in the thickest part, away from bone and fat.
Formula
total time (min) = 1 inch base time x square root of thickness in inches x method factor. The 1 inch base times are 7 minutes for rare, 9 for medium rare, 10.5 for medium and 13 for well done. The method factor is 1 for a grill and 1.2 for sear then roast. Rest time is 5 minutes. Target centre temperatures are 52 C rare, 63 C medium rare, 71 C medium and 77 C well done.
Worked example
A 2.54 cm (1 inch) steak cooked medium rare on a grill takes 9 x square root of 1 x 1 = 9 minutes, turned once at the halfway point. A 3.81 cm (1.5 inch) steak at medium takes 10.5 x square root of 1.5 = 12.9 minutes, so about 13 minutes. A 5.08 cm (2 inch) steak at well done, seared and finished in the oven, takes 13 x square root of 2 x 1.2 = 22.1 minutes. Rest every steak for 5 minutes before cutting.
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Frequently asked questions
Should I cook a steak from room temperature?
It makes less difference than the thickness does. A steak taken from the fridge will be a little cooler at the centre after the same time, so start checking later or add a minute. The bigger gains come from drying the surface before cooking and resting afterwards.
Why does the page scale time by the square root of thickness?
It is a fitted description of published charts between about 0.75 and 2 inches. Heat conduction alone would scale with the square of thickness, but in a real pan or grill the hot surface, the turning and the resting all blunt that, so the square root reproduces the tested times better and is described here as a fit rather than a law.
What is the safe temperature for steak?
Health Canada lists 63 C (145 F) for medium rare beef steaks and roasts, 71 C (160 F) for medium and 77 C (170 F) for well done. The USDA uses 145 F with a three minute rest for whole cuts of beef. A rare steak at 52 C is below both figures.
Does a bone change the time?
Yes. Bone conducts heat differently from meat and can also sit against the thermometer, so a bone in steak needs the probe moved away from the bone. The times here assume a boneless steak of even thickness.