I just made a count and discovered that I have eight thermometers in my kitchen. There's a reason for that, and no, it's not because I have a thing for thermometers. Rather it's because no single gadget can so improve your cooking as precise control of heat - and cold.
I have two refrigerator thermometers (compare prices), two oven thermometers (compare prices), a digital instant-read thermometer, a digital remote-probe thermometer (also instant-read), an analog instant-read thermometer(compare prices), and a room thermometer.
To keep food safe it must be stored below 40 degrees F (4C) or above 140 degrees F (60C). This means you need to keep your refrigerator below 40 degrees. You should also note that your fridge has warmer and cooler areas. Generally top-front is the warmest, so track the temperature there. Also, keep in mind that a loaded refrigerator restricts air flow and so even though the high is usually 40F, it may be higher than that before a party. Frozen food should be kept below 0 degrees F (-18C) and the same caveats about loading the refrigerator apply to the freezer.
I haven't used my oven thermometers at home since I first checked my oven for calibration and I have two because I didn't believe the first one. (By the way, in general I prefer spirit thermometers - the kind with a glass tube - for the fridge and oven as opposed to bi-metal - dial - thermometers because they're more accurate.) Once your oven is calibrated you can store the oven thermometer.
Instant-read thermometers are critical to cooking meat to the desired (and a safe) temperature. I use my digital remote-probe thermometer when cooking roasts and steaks. It has a feature that allows me to tell it to beep when the temperature reaches a particular point, then I'll use my other digital thermometer to spot check the temp in other places. In point of fact I could also use the probe to do this, but because I have the other thermometer I use it.
Lastly, knowing the temperature of the kitchen is great help when I bake bread because it enables me to better control rising times. If the kitchen is really cool then I let bread rise in the oven with a light bulb, if the kitchen is really warm I let the bread rise in a cooler place in the house.
You don’t need as many thermometers as I have. In fact, I don't need as many thermometers as I have. At a minimum I would recommend a refrigerator thermometer, an oven thermometer if you're not sure your oven is correct (and I've only had one oven that was) and a digital instant-read remote-probe thermometer. But at minimum, you should have a digital instant-read thermometer - it's well worth what you pay for it in perfectly cooked steaks, roasts, chops and chicken.
