What Size Heater Do I Need For My Garage?


A garage heater is a perfect equipment to install in your garage especially if you’ll be working for hours in a garage during a cold season. As important as garage heaters are, you need to be careful that you do not choose the wrong size for your garage space. Therefore, you need to be decisive enough to carefully choose the right size. For if you buy too small a model, it will be inefficient and won’t give out the sufficient and needed amount of warmth. Not only that. If on the other hand, you end up getting too large a type, you are only shelling out more money than what is necessary. Therefore, sit back and carefully read along as you’ll be able to find points that will help you when it comes to choosing the right size of heater that will give you adequate and sufficient heat in the winter season.

Way to Determine the Size of Garage Heater you need

There are numerous ways to know the actual thermal output that your garage heater emits for complete performance.

The Easy Method

The first way is very easy and it’ll be a wise move to learn about this method before actually deciding to go for the method of calculation. Measure out the length and width of your garage space and multiply the numbers. For example, if the length of your garage measures 30 feet in length and 30 feet in width. Simply multiply 30 by 30. Therefore, your garage has an area of 900 square feet. Now that you know the size of your garage, go online, and search for the best models you want. Since most manufacturers specify the number of square meters a particular heater can cover, it makes it easier for you to search and find the type that’ll fit in your garage.

If your garage is about 900 square feet like the example given above, you should purchase a garage heater that a little bit larger than the actual size of your garage. Probably something around 1000 square feet. Purchasing a heater that is a little larger, prepares you for those very cold days by allowing a safety cushion. Don’t forget that if your garage lacks sufficient insulation, you should consider a model that will conveniently handle a larger area to get rid of the loss of heat that the insulation might bring about.

The Calculating Method

If the model you’re searching is not specifying the actual size of the area that the unit will cover, or if you want a definitive exact answer, go for the easy formula. You’ll only need a paper to calculate on, a pencil to write with, a tape measure, and yes! A calculator. Determine first the square footage of your garage space. By following the above method. Multiply the length by the width. This means if your garage space is 25 feet in length and 10 feet in width, the calculation would simply be 20 × 10 = 200 square feet. Now, you need to take into consideration the total area of your garage. You need to know the cubic feet. How do you do this? Simply measure the height of the ceiling. Then multiply it with the square footage you just calculated. Just like the previous example, if the height of the ceiling is about 15 feet. Then your calculation will be, (the square footage) 200 × 15(the height of the ceiling) = 3000 cubic feet.

You now need to find the rise of temperature that you would want your garage to accommodate. How do you do this? Take the smallest temperature that is a norm where you reside during winter and then deduct it from the temperature you want to maintain in the garage. This means if the lowest temperature of the area you reside is about 29 degrees Fahrenheit and you want a temperature of about 59 degrees to be consistent. Simply deduct 59 – 29 = 30.

To attain the temperature rise, you’ll need to calculate the British Thermal Units (BTUs). First, get to know the insulation level in your garage. The garage’s insulation is imperative. So don’t discard it. Because you might need to work in areas like retention of heat loss.

Use the following as a variable, make use of these numbers for the insulation of the garage. If the garage has a very small amount of insulation, use 1.5. On an average level, you should make use of 1 for the insulation and if the insulation of the garage is quite big, you should use 0.5. After arriving at this number, you’ll have to multiply. The insulation variable Will be multiplied by the cubic feet of the height.

This is where the division comes in. Divide the number by a British Thermal Units (BTUs) factor of 1.6. This will help you arrive at the needed BTUs. Back to the earlier example. If by chance, your garage has a small amount of insulation, you’ll make use of 1.5 × height × temperature ÷ BTU factor (1.6). So,(1.5 × 3000 × 30) / 1.6 = 84,375 BTU.

As a safety margin, don’t forget you’ll need to add a buffer to the answer. This guarantees your garage heater to work efficiently even when days are colder than expected. To calculate this, add 10% to your BTU answer. Back to the example again, go through these steps. Find if multiplying 10 is equal to 10% of the BTU. Here comes the calculation, 84,375 × 10/100 = 8,437.5. Now add the answer to the real BTU answer. Like, 84,375 + 8,437.5 = 92,812.5 . And you’ve just calculated the hourly BTU output, 92,812.5. Watch this video to learn more about the calculation.

Installing the Garage Heater

After knowing how to calculate the amount of BTUs that the garage heater requires to work, it should then be installed. The unit’s ability to heat the garage should be optimal. Do this by installing your garage heater in such a way that it will be facing the entrance when placed at the back wall. The highly insulated area in the garage is the best place for heat to come from and the best place to lose heat.

Whatever type of heater you get, be sure that any objects within 3 to 4 feet of the unit are removed. So that those objects do not overheat and never forget to have a clear path especially if you do have a forced-air model. It makes the air produced by the garage heater to go round the workplace keeping it warm all time.


To figure out the right size of the heater to use in a garage might sound hard or difficult. But getting the necessary equipment like a calculator, a tape measure, paper, and a pencil you’ll be able to calculate and get a perfect size. While it is advisable to use the simpler method, if you are the meticulous type, then you may opt for the long calculation method. By and large, do well to choose the right type of heater to keep your garage warm during cold days.