Appliance Gas Load Calculator — Total Household BTU/hr
Add up every gas appliance to get the total connected load in BTU/hr — the single number that drives gas-pipe sizing.
Calculator
Your connected appliances total 207,000 BTU/hr (about 207.0 CFH on natural gas). Use this total to size the gas line. ⚠️ Gas work must be done by a licensed professional with a permit and inspection.
Before anyone can size a gas line, you need the total connected load: the sum of the input ratings of every appliance the line will feed, in British Thermal Units per hour (BTU/hr). Sizing tables — like the NFPA-54 / IFGC longest-length method — start from this figure, so getting it right is the first step of any gas project. This calculator simply adds your appliances together and also shows the load in CFH (cubic feet per hour), the unit the capacity tables actually use.
Use each appliance's input rating from its data plate or manual — not its output or its efficiency-adjusted heat. Input is what the pipe has to deliver. If two ranges of the same brand differ, trust the label on your unit. When you plan for the future (say, a pool heater or a second furnace you might add later), include it now so the pipe you run has headroom.
Formula
The connected load is a plain sum:
total BTU/hr = furnace + water heater + range + dryer + other
To express it in cubic feet per hour on natural gas (≈ 1000 BTU per cubic foot):
CFH = total BTU/hr ÷ 1000
On propane (≈ 2516 BTU per cubic foot) you would divide by 2516 instead — see the BTU to CFH converter.
Worked example
Take a typical all-gas home:
- Furnace: 80,000 BTU/hr
- Water heater: 40,000 BTU/hr
- Range: 65,000 BTU/hr
- Dryer: 22,000 BTU/hr
- Other: 0
Adding them gives 80,000 + 40,000 + 65,000 + 22,000 = 207,000 BTU/hr, or about 207 CFH on natural gas. That 207,000 BTU/hr total is what you carry into the gas pipe size tool along with the longest run to the farthest appliance.
How the connected load is used
Two subtleties trip people up. First, the load a branch carries is only the appliances downstream of it, while the main carries everything — you size each segment for the load it actually feeds, which is why a plan usually lists several loads, not one. Second, in practice a house rarely runs every appliance at full fire simultaneously, but codes size the pipe for the full connected load anyway, giving a built-in safety margin. Do not "diversify" the load yourself; use the full sum.
Natural gas is delivered to homes at low pressure (commonly about 7 in WC, roughly 0.25 psi), so the pipe has to be generous — there is very little pressure to push a lot of gas through a small line. Propane systems often run at 11 in WC or on a 2-psi / regulated design, which changes the tables. Either way, the total load you compute here is the starting input.
Reference table
Typical nameplate input ratings — always read the rating plate on your own appliance, since models vary widely. Labeled planning typicals.
| Appliance | Typical input (BTU/hr) |
|---|---|
| Forced-air furnace | 60,000 – 120,000 |
| Tank water heater | 30,000 – 50,000 |
| Tankless water heater | 120,000 – 199,000 |
| Range / cooktop + oven | 40,000 – 65,000 |
| Clothes dryer | 20,000 – 25,000 |
| Gas fireplace / log set | 25,000 – 40,000 |
| Boiler (hydronic) | 80,000 – 200,000 |
| Pool / spa heater | 100,000 – 400,000 |
| Barbecue / outdoor kitchen | 40,000 – 90,000 |
Frequently asked questions
What is a gas appliance load?
It is the total amount of gas your appliances can burn at once, measured in BTU/hr (British Thermal Units per hour). You get it by adding up the input rating printed on each appliance's data plate. It is the first number needed to size a gas line.
Should I use the input or output rating?
Use the input rating. Input is the gas the appliance consumes and therefore what the pipe must deliver; output is the useful heat after efficiency losses and is always lower. Sizing on output would undersize the pipe.
How do I convert the total to CFH?
Divide by the fuel's heating value: about 1000 BTU per cubic foot for natural gas, or 2516 for propane. So 207,000 BTU/hr is about 207 CFH on natural gas. The BTU to CFH converter does this for you.
Do I include appliances I might add later?
It is wise to. If a future pool heater, second furnace or outdoor kitchen is likely, add its load now so the line you run has capacity. Re-running gas pipe later is far more expensive than oversizing a little up front — but confirm the plan with a licensed gas fitter.
Is the whole house on one pipe size?
No. The main near the meter carries the full connected load, while each branch only carries the appliances beyond it, so branches are usually smaller. A gas plan lists the load and length for every segment.