Kitchen thermometer

The kinds

Instant-read digital probe

The one to buy. A thin probe and a reading in two to four seconds. Use it for meat, bread, fish, oil, custard — everything.

Leave-in probe with a cable

The probe stays in the food and the display sits outside the oven, often with an alarm. Excellent for a large joint or an overnight cook.

Oven thermometer

A dial that sits on the shelf. Most domestic ovens are out by 10 to 20°C, and this is the cheapest way to find out by how much. Arguably the highest-value item on this list.

Sugar or jam thermometer

A high-range thermometer that clips to the pan. Necessary for caramel and confectionery, where the temperature is the recipe.

Infrared gun

Reads surface temperature only. Useful for a pan or a griddle, useless for the inside of anything.

Dial bimetallic

Slow, imprecise, and needs recalibrating. Superseded by cheap digital probes.

What it actually improves

• Meat and poultry. The single biggest use. FoodHQ does not publish safe internal temperatures — the Food Standards Agency does, and a thermometer is how you meet them.
• Bread. A baked loaf has a characteristic internal temperature, and it is far more reliable than tapping the base and listening.
• Deep frying. Oil temperature decides whether food crisps or soaks. This is where a thermometer pays for itself in one meal.
• Custards and curds. They thicken and curdle within about ten degrees of each other.
• Caramel and sugar work. Soft ball, hard crack and the rest are temperatures, not appearances.
• Your oven. Almost every oven lies, and knowing by how much explains a great deal of past disappointment.

Using it properly

• Aim for the thickest part, away from bone, fat and the pan, which all read differently from the meat.
• Go in from the side for thin pieces, so the probe sits in the middle rather than passing through.
• Take several readings. The first one might have found a pocket of fat.
• Read the residual rise. A large joint continues to rise several degrees after it leaves the oven, so it comes out below the target.
• Calibrate it occasionally. In iced water it should read 0°C and in boiling water 100°C, adjusted for altitude. If it is out, most digital probes can be reset.
• Clean the probe between uses, especially between raw and cooked food.

Why the proxies are unreliable

The traditional doneness tests are all indirect. Poking meat and comparing the firmness to the base of your thumb depends on the cut, the fat content and the shape. Cutting into it to look lets the juice out and tells you about one spot. Timing assumes your oven, your pan and your piece of meat match the ones in the recipe, and at least one of those is always different.

A thermometer measures the thing the cooking is actually controlling. It also teaches you the proxies faster than anything else, because you can poke the meat and then check what that firmness corresponded to — after a dozen roasts you will need the thermometer less.

Common questions