Heating BTU Calculator: How Many BTUs Per Square Foot? (2023)

Question: How many BTUs do I need to heat 1500 sq ft? How many square feet will 30,000 BTU heat?

Example: To heat 1500 sq ft home, you will need anywhere between 45,000 BTU and 90,000 BTU.

These kinds of questions are very common when planning your heating needs. Adequately estimating how many BTUs you need to heat up your home is essential. The purpose of the ‘Heating BTU Calculator’ below is to pinpoint how many BTUs of heat your need as precisely as possible.

BTU or ‘British Thermal Unit’ is a unit of heat. 1 BTU is enough heat to raise the temperature of 1 pound of water by 1°F. US households require anywhere from 20,000 BTU to 300,000 BTU of heating output in the winter.

To calculate how many BTU of heating output you need, you have to know only 3 factors:

  1. Total square footage of your home, or the place you want to heat up in winter. This can be anything from a 150 sq ft room to a 3,000+ sq ft house.
  2. Your climate zone. Heating a house in Miami, Florida will obviously require less heating BTUs than heating a house in Chicago, Illinois.

To use the heating BTU calculator, you will first need to measure the place you want to heat up. You need to know if you’re heating up a 1000 sq ft, 1500 sq ft, or a 3000 sq ft home, or a 400 sq ft room, for example.

Secondly, you need to figure out what climate zone you live in. That will determine how many BTU per square foot you need for heating (more on that later on). The United States is divided into 7 main climate zones or regions. Example: Miami, Florida, is in Climate Zone 2 and requires 35 BTU of heat per sq ft. Chicago, Illinois, is in Climate Zone 5 and requires 50 BTUs of heat per square foot.

To help you figure out which climate zone you should input into the heating BTU calculator, you can use this map by Office of Energy Efficiency & Renewable Energy:

(Video) How Much BTU Heat Do I Need? Try This Formula

Heating BTU Calculator: How Many BTUs Per Square Foot? (1)

With this information, you can use the Heating BTU Calculator to get a basic idea of how many BTUs you need to heat your home.

We will also explain how many square feet does a heater (furnace, space heater, etc.) with certain BTU output heat. On top of that, we will solve a few heating BTU examples below, and if you don’t find an answer, you can use the comment section and we’ll try to help you out.

Here is this handy and simple-to-use calculator for heating BTUs:

Heating BTU Calculator (Insert Sq Ft And Climate Zone)

Here is a short example of how this calculator works:

Let’s say you have a 1,200 sq ft home in Nashville, Tennessee. You’re trying to figure out how many BTU should a furnace or a central heating system produce to adequately keep your home warm during winter.

Before using the heating BTU calculator, you consult the climate zone map above and see that Nashville falls into the Climate Zone 4 region. With that, you can insert both 1,200 sq ft and ‘Climate Zone 4’ into the calculator and get the estimate of how many BTU you would need to keep your home adequately heated like this:

Heating BTU Calculator: How Many BTUs Per Square Foot? (2)

As you can see, the best estimate is that you will require 54,000 BTU of heating during the winter season.

(Video) Simple Calculating of BTU Per Square Foot

Now, there are two kinds of questions people ask when calculating the heating BTU. These are:

  1. How many BTUs do I need to heat X square feet? X designates the size of a home; usually between 500 and 5,000 BTUs.
  2. How many square feet will X BTU heat? X here designated the numbers of BTUs (British Thermal Units). This is a very relevant question when deciding about the size of space heaters; not furnaces or central heating systems. Normally, we speak anywhere from 1,000 BTU to 30,000 BTU here.

To help you get some answers, we have calculated two heating BTUs tables for each question:

How Many BTUs Do I Need To Heat My Home? (Table 1)

Using the BTU heating calculator, we can estimate how much heating output you require to heat a home with certain square footage.

To help you out, we’ve gathered the heating BTU requirements for 500 sq ft to 5,000 sq ft homes.

These BTU requirements have, depending on where in the US you live, quite a large interval. Example: How many BTU do I need to heat 1,500 square feet?

Answer: 45,000 BTU – 90,000 BTU. The exact number depends on where you live. If you live in Climate Zone 1 (very hot climate), you will require 45,000 BTU. If you live near the Canadian border – Climate Zone 7 (very cold climate), you’ll need 90,000 BTU. Most people live somewhere in between and will require around 67,500 BTUs. We’ll designate that as the “standard climate” in the BTU heating table below:

Heating BTUs Table (Rough Estimates)

Home Size (Heating):Standard ClimateVery Cold ClimateVery Hot Climate
500 square feet22,500 BTU30,000 BTU15,000 BTU
1000 square feet45,000 BTU60,000 BTU30,000 BTU
1500 square feet67,500 BTU90,000 BTU45,000 BTU
2000 square feet90,000 BTU120,000 BTU60,000 BTU
2500 square feet112,500 BTU150,000 BTU75,000 BTU
3000 square feet135,000 BTU180,000 BTU90,000 BTU
3500 square feet157,500 BTU210,000 BTU105,000 BTU
4000 square feet180,000 BTU240,000 BTU120,000 BTU
4500 square feet202,500 BTU270,000 BTU135,000 BTU
5000 square feet225,000 BTU300,000 BTU150,000 BTU

How Many Square Feet Will 1,000 – 30,000 BTU Heat?

In much the same way, we can answer how many square feet will a heater with certain heating output (expressed in BTU) heat.

Heating Output:Square Footage (Standard Climate)Square Footage (Very Cold Climate)Square Footage (Very Hot Climate)
1,000 BTU22,2 sq ft16,6 sq ft33,3 sq ft
3,000 BTU66,6 sq ft33,3 sq ft100 sq ft
5,000 BTU111,1 sq ft83,3 sq ft166,6 sq ft
10,000 BTU222,2 sq ft166,6 sq ft333,3 sq ft
15,000 BTU333,3 sq ft250 sq ft500 sq ft
20,000 BTU444,4 sq ft333,3 sq ft666,6 sq ft
25,000 BTU555,5 sq ft416,6 sq ft833,3 sq ft
30,000 BTU666,6 sq ft500 sq ft1000 sq ft

Now you can answer how many square feet will a 5,000 BTU heat. On average, it can heat about a 110 sq ft room. In the cold north, 5,000 BTU will be enough to heat 80 sq ft, and in the hot south, you will be able to heat a 170 sq ft room with such a space heater.

(Video) BTU Calculations

Let’s look at one example:

How Many Square Feet Will 40,000 BTU Heat? (Example)

Let’s say we have a 40,000 BTU heater (it could be a house heater or a 40,000 BTU patio heater).

Let’s also presume we live in a standard climate (Climate Zone 3). In this climate zone, you will need about 40 BTU to heat 1 sq ft of space.

Here’s how many square feet can a 40,000 BTU heat:

Area = 40,000 BTU / 40 BTU per sq ft = 1,000 sq ft

In a standard climate, 40,000 BTU is enough to heat a 1,000 sq ft area. Obviously, if you live in colder climate, a 40,000 BTU heater will heat an area below 1,000 sq ft. If you live in a warmer climate, 40,000 BTU will heat more than 1,000 sq ft area.

The key question, as you can see, is in which Climate Zone you live. Based on Climate Zone, you know how many BTU of heat you need per square foot.

Let’s have a look at how many BTU of heat you need in a specific Climate Zone:

(Video) How to Determine Your Furnace BTU Size

How Many BTU Of Heat Do You Need Per Square Foot? (Depends On Climate Zone)

To create a heating BTU calculator, you need to know how many BTU of heat per square feet you need in a certain climate zone. Obviously, in the cold north, you will need more BTUs per square foot than in the warm south. How many BTUs exactly?

Here is a neat table with heating BTUs per square foot for all 7 Climate Zones (check the heating map above with Climate Zones for reference):

Climate ZoneBTUs Per Sq Ft
Climate Zone 130 BTU per sq ft
Climate Zone 235 BTU per sq ft
Climate Zone 340 BTU per sq ft
Climate Zone 445 BTU per sq ft
Climate Zone 550 BTU per sq ft
Climate Zone 655 BTU per sq ft
Climate Zone 760 BTU per sq ft

As you can see, in the north, you need about double the heating output to heat 1 square foot compared to the extreme south.

Example: With 35,000 BTU, you can heat a 1,000 sq ft home in Florida. If you’re from Chicago, a 35,000 BTU heater will adequately heat a 600 sq ft home.

You can also check a similar BTU calculator for air conditioning here.

If you need additional advice, you can give us some insight into how big a home you need to heat and where, and we’ll do our best to help you out with the heating BTU calculation.

Table of Contents

(Video) BTU Calculations
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