Tent Heater Calculator: BTUs, Heaters and Fuel for Event Tents
Enter your tent's size and heights, the outside and target temperatures, how closed in the tent is and the heater you're renting. Get the BTUs per hour to heat it, how many heaters you need, and how much propane or diesel to order for the event. A planning estimate to take to your heater supplier.
Size the Heat for Your Event Tent
218,400 BTU/hr
Heat needed
To warm 31,200 cubic feet by 35°F at a 0.2 factor.
2
Heaters needed
240,000 BTU/hr delivered together.
3.3 gal
Fuel per hour
Propane, all heaters at full fire.
98.4 gal
Fuel for the event
Over 30 heating hours.
| Floor area | 2,400 sq ft |
|---|---|
| Average height | 13 ft |
| Tent volume | 31,200 cu ft |
| Temperature rise | 35°F |
| Heat from each heater | 120,000 BTU/hr |
The formula
Length × width × (sidewall + peak) ÷ 2 = tent volume.
Volume × temperature rise × heat-loss factor = BTU per hour.
BTU per hour ÷ (heater rating × efficiency), rounded up = heaters.
Heaters × rating ÷ BTU per gallon × hours = fuel.
Rough planning estimate, not safety or code advice. The factors are rules of thumb. Use indirect-fired, vented heaters with the burner outside for an occupied tent; your heater supplier sizes and places them and the fire marshal approves the setup. Build heating into your event safety plan and ask the tent company the questions to ask a tent rental company about heating and sidewalls.
How the Tent Heater Calculator Works
1. Work out the tent’s volume
Multiply length by width by the average of the sidewall and peak heights. A 40 x 60 ft tent with 8 ft sidewalls and an 18 ft peak holds 31,200 cubic feet. Not sure of the size yet? Start with the event tent size calculator.
2. Set the temperature rise
Subtract the coldest outside temperature you expect from the temperature you want inside. A winter market where shoppers keep coats on can aim lower than a seated dinner.
3. Pick how closed in the tent is
Sidewalls, a floor and closed doors hold heat; open sides let it blow away. The factor turns volume and temperature rise into BTUs per hour.
4. Count heaters
Divide the heat needed by what one heater delivers (its rating times its efficiency) and round up. Spread several smaller heaters around a long tent rather than relying on one big unit.
5. Order fuel and power
Fuel is planned at full fire for every heating hour, so it is a ceiling. Most indirect-fired heaters also need electricity for the fan and controls; add them to the event power calculator along with vendor and lighting loads.
Heating is a safety item, not just a comfort one. Put heater positions, fuel storage, clearances and carbon monoxide checks in your event safety plan, and confirm sidewalls, flooring and heater placement with the questions to ask a tent rental company.
Enclosure Factors Used
Rough planning rules of thumb, in BTU per hour per cubic foot per degree F. They are not a standard or a test result: your heater supplier sizes the real system and the fire marshal approves it.
| Enclosure | Factor |
|---|---|
| Sidewalls plus floor or linerAll sidewalls down, with a floor or liner and doors kept closed. | 0.133 |
| Sidewalls, no floorAll sidewalls down on bare ground or grass, doors opening often. | 0.2 |
| Open or partly open sidesOpen or partly open sides. Spot heat only: the tent may never reach the target. | 0.4 |
Indirect-Fired Heaters for Occupied Tents
For a tent with people in it, plan on indirect-fired, vented heaters: the burner and fuel sit outside and a duct brings warm, clean air in while the exhaust vents away. Direct-fired and unvented heaters release combustion gases into the space. Ask the supplier about thermostats, ducting, fuel tank placement and refills, and ask the fire marshal what permit or inspection applies. This is not safety or code advice.
Map Tents, Heaters and Vendor Spaces with Map D
Map D doesn’t size heaters or replace your supplier’s plan. It helps you lay out the site around them: in Map D’s floor plan editor you can set the map to your site’s size, mark each tent with a rectangle area, and place vendor booths, aisles and named areas for heater and fuel tank positions, all drawn to scale. Running a holiday market or winter festival? Our festival management software puts vendor spaces on the same map, and any site plan starts in our event floor plan software. You can build one event’s floor plan free; publishing it needs a paid plan, from $1,500 per event.
Heat Needed for Common Tent Sizes
Each size at this calculator’s defaults: a 35°F rise (30°F outside to 65°F inside), sidewalls with no floor (0.2) and 150,000 BTU/hr heaters delivering about 120,000 each. Heights are examples with an 8 ft sidewall; use your tent’s spec sheet and the calculator above for your own figures.
| Tent size | Example peak | Volume, cu ft | BTU/hr | Heaters |
|---|---|---|---|---|
| 20 x 20 ft | 12 ft | 4,000 | 28,000 | 1 |
| 20 x 40 ft | 13 ft | 8,400 | 58,800 | 1 |
| 30 x 30 ft | 15 ft | 10,350 | 72,450 | 1 |
| 30 x 60 ft | 16 ft | 21,600 | 151,200 | 2 |
| 40 x 60 ft | 18 ft | 31,200 | 218,400 | 2 |
| 40 x 80 ft | 18 ft | 41,600 | 291,200 | 3 |
| 60 x 100 ft | 22 ft | 90,000 | 630,000 | 6 |
What this assumes
Every figure the calculator starts with, and where it comes from. Where the honest answer is that a number depends on your venue, it says so rather than inventing one.
- Tent volume
- Length x width x the average of the sidewall and peak heights, in cubic feet. The default 40 x 60 ft tent with 8 ft sidewalls and an 18 ft peak is an example; take the real heights from the rental company's spec sheet. Heat rises, so a tall peak adds volume you pay to heat.
- Temperature rise
- Target inside temperature minus the coldest outside temperature you expect while the tent is open. Defaults are 30 F outside and 65 F inside, a 35 F rise. Use the overnight low if the heaters run before doors open, and plan for wind on top.
- Enclosure (heat-loss) factor
- A rule-of-thumb factor for how fast warm air escapes, in BTU per hour per cubic foot per degree: 0.133 closed up with sidewalls and a floor or liner, 0.2 with sidewalls on bare ground (the default) and 0.4 with open or partly open sides. They are this calculator's planning figures, not a standard or a test; type your supplier's factor if they give you one.
- Heater rating and efficiency
- Each heater's rating in BTU per hour of fuel burned (150,000 by default, for example; 170,000 is another size you'll see) and the share delivered into the tent as heat (default 80%). Check the supplier's spec sheet: some list input and output separately.
- Fuel
- All heaters at full fire for every heating hour, the most they can burn: 10 hours a day for 3 days by default, preheat included. Propane holds about 91,500 BTU per gallon and diesel or heating oil about 138,500 (approximate heating values). Thermostats cycle the heaters, so actual use is usually lower.
What it does not model
- Safety and permits. This is not safety or code advice. Occupied tents should be heated with indirect-fired, vented heaters with the burner and fuel outside the tent, placed and ducted by the supplier. The fire marshal or local authority may require a permit, inspection, clearances and fuel-storage rules; ask before you book.
- Wind, rain and snow. Wind strips heat from tent fabric fast, and snow load is a structural question for the tent company, not a heating one.
- Doors and traffic. A market or festival tent with doors open all day behaves closer to the open-sides factor than the sidewalls one.
- People, lights and cooking. A packed tent warms itself, and food vendors add heat (and ventilation needs). The calculator ignores both, which errs on the warm side.
- Electrical power. Most indirect-fired heaters need power for the fan and controls; add them to your generator or power plan.
Estimate only, from the figures you entered. Not a quote. Last reviewed November 2026.
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Frequently asked questions
How many BTU does it take to heat a tent?
Multiply the tent's volume in cubic feet by the temperature rise you need and a heat-loss factor for how closed in the tent is. At this calculator's defaults, a 40 x 60 ft tent with an 8 ft sidewall and 18 ft peak (31,200 cubic feet), warmed 35 F with sidewalls down at a 0.2 factor, needs about 218,400 BTU per hour. Fully closed with a floor (0.133) it is about 145,000; with open sides (0.4) about 437,000.
How many heaters do I need for a 40x60 tent?
At this calculator's defaults, 2 heaters rated 150,000 BTU/hr: the tent needs about 218,400 BTU per hour and each heater delivers about 120,000 at 80% efficiency. On a colder day, with open sides or a taller peak you may need 3 or 4. Ask your supplier whether to add a spare in case one fails.
How much fuel does a tent heater use?
Two heaters rated 150,000 BTU/hr burn about 3.3 gallons of propane an hour between them at full fire (2 x 150,000 / about 91,500 BTU per gallon), or about 2.2 gallons of diesel. Over 10 hours a day for 3 days that is about 98 gallons of propane or 65 of diesel. Thermostats cycle the heaters, so this is a ceiling to order against; the supplier confirms tank sizes and refills.
What kind of heater should I use in an event tent?
For a tent with people inside, plan on indirect-fired heaters: the burner sits outside and ducts warm, clean air in, while the exhaust vents outside. Direct-fired and unvented heaters put combustion gases into the space. The heater supplier and the fire marshal decide what is allowed and where it goes.
Can I plan tents and heaters on the site map in Map D?
Yes, for the layout. In Map D's floor plan editor you can set the map to your site's size, mark each tent with a rectangle area and lay out vendor booths, aisles and named areas for heater and fuel tank positions, all drawn to scale. Map D doesn't size heaters or replace your supplier's plan. You can build one event's floor plan free; publishing it needs a paid plan, from $1,500 per event.
Sources
- US Energy Information Administration: British thermal units (heat content of propane, heating oil and diesel) · checked 2026-11-09
- Map D help center: the free plan and how to upgrade · checked 2026-11-09
- Map D pricing · checked 2026-09-18