Propane Usage Calculator: How Long Will Your Tank Last? (2026)
Running out of propane halfway through a backyard gathering is one of those avoidable frustrations that a single calculation eliminates entirely. Whether you run a propane fire pit on weekend evenings, host on a gas patio heater all season, or use a fire table as your outdoor centerpiece, the math behind fuel consumption takes under a minute once you know your appliance's BTU rating.
This propane gas usage calculator takes your BTU output, session length, and tank size and returns gallons per hour, cost per session, and exactly how many uses you get before a refill.
Below the widget you will find worked examples for the three most common outdoor propane appliances, a full reference table by BTU range, and a dedicated section covering propane use calculator logic for fire tables and patio heaters.
Quick Takeaways
- One gallon of liquid propane contains approximately 91,500 BTU of energy (per U.S. Energy Information Administration data)
- A 50,000 BTU fire pit burns roughly 0.55 gallons per hour
- A standard 20 lb tank holds 4.7 gallons, giving about 8.5 hours at 50,000 BTU
- Your BTU rating is printed on the appliance label or product spec sheet
- Gas fire tables range from 40,000 to 90,000 BTU, which is a wider spread than most patio heaters
- Running at half output roughly doubles runtime without any hardware changes
- A 100 lb cylinder holds 23.6 gallons and suits anyone using a fire pit three or more evenings per week
How the Propane Usage Calculator BTU Formula Works
Every propane use calculator relies on one constant: a gallon of propane releases approximately 91,500 BTU when burned. The EIA propane energy data confirms this figure, which has been the standard used by appliance manufacturers for appliance efficiency ratings for decades.
The four-step calculation is:
Step 1: Find your appliance's BTU/hr rating on the product label or spec sheet.
Step 2: Divide BTU/hr by 91,500 to get gallons burned per hour. A 60,000 BTU fire pit burns 60,000 / 91,500 = 0.66 gallons per hour.
Step 3: Multiply gallons per hour by session length (hours) to get gallons per session.
Step 4: Divide your tank's total gallon capacity by gallons per session to find sessions per tank.
That last output, sessions per tank, is what this calculator adds beyond the single-output tools most competitor sites offer. It tells you not just burn rate but how many evenings you can plan before a refill.
For gas fire pits with a valve that adjusts output, always check the maximum BTU rating first, then plan around 60 to 70 percent of that figure for a realistic medium-flame session.
Worked Examples
Example 1: 50,000 BTU Fire Pit on a 20 lb Tank
A mid-range propane fire pit rated at 50,000 BTU per hour is one of the most common outdoor setups.
Inputs: 50,000 BTU/hr, 3-hour evening session, 20 lb tank (4.7 gallons), $3.50/gallon
Math:
Gallons per hour: 50,000 / 91,500 = 0.55 gal/hr
Gallons per session: 0.55 × 3 = 1.64 gallons
Cost per session: 1.64 × $3.50 = $5.73
Sessions per 20 lb tank: 4.7 / 1.64 = 2.9 sessions
Takeaway: A 20 lb tank fuels roughly three evenings at this output. For anyone using a gas fire pit two to three nights per week, a single spare tank in rotation prevents mid-session interruptions.
Example 2: 65,000 BTU Gas Fire Table on a 100 lb Tank
Gas fire tables are the fastest-growing outdoor fire category, with output ratings spanning a wider range than either fire pits or patio heaters. For this example, assume a standard mid-range gas fire table at 65,000 BTU.
Inputs: 65,000 BTU/hr, 2.5-hour evening session, 100 lb tank (23.6 gallons), $3.50/gallon
Math:
Gallons per hour: 65,000 / 91,500 = 0.71 gal/hr
Gallons per session: 0.71 × 2.5 = 1.78 gallons
Cost per session: 1.78 × $3.50 = $6.22
Sessions per 100 lb tank: 23.6 / 1.78 = 13.3 sessions
Takeaway: A 100 lb cylinder carries over 13 evening sessions before a refill, making it well-suited for entertaining households that host several times per week.
Example 3: 40,000 BTU Patio Heater on a 20 lb Tank
Standard freestanding gas patio heaters typically rate between 30,000 and 46,000 BTU per hour. At the common 40,000 BTU mark:
Inputs: 40,000 BTU/hr, 3-hour session, 20 lb tank (4.7 gallons), $3.50/gallon
Math:
Gallons per hour: 40,000 / 91,500 = 0.44 gal/hr
Gallons per session: 0.44 × 3 = 1.31 gallons
Cost per session: 1.31 × $3.50 = $4.59
Sessions per 20 lb tank: 4.7 / 1.31 = 3.6 sessions
Takeaway: A 20 lb cylinder covers about three to four patio heater sessions, which lines up closely with fire pit usage at similar output levels. High-BTU patio heaters rated at 46,000 BTU or above will burn approximately 15 to 20 percent faster at full output.
Propane Appliance Reference Table
| Appliance | Typical BTU Range | Gallons/Hour | 20 lb Runtime | 100 lb Runtime |
|---|---|---|---|---|
| Fire pit (low-mid) | 30,000–50,000 | 0.33–0.55 | 8.6–14 hrs | 43–72 hrs |
| Fire pit (mid-high) | 50,000–70,000 | 0.55–0.77 | 6.1–8.6 hrs | 30–43 hrs |
| Gas fire table | 40,000–90,000 | 0.44–0.98 | 4.8–10.7 hrs | 24–54 hrs |
| Standard patio heater | 30,000–46,000 | 0.33–0.50 | 9.4–14 hrs | 47–72 hrs |
| High-BTU patio heater | 46,000–65,000 | 0.50–0.71 | 6.6–9.4 hrs | 33–47 hrs |
All runtime figures assume a full tank at maximum rated output. Medium-flame operation typically extends runtime by 40 to 60 percent.
What Your Propane Tank Calculator Results Mean
Gallons per hour is the core output. If this number surprises you, compare it against your last refill receipt volume divided by total runtime hours to verify your BTU estimate is accurate.
Sessions per tank is the number most buyers find most useful. It converts abstract fuel math into a concrete refill schedule. If sessions per tank falls below three, a larger cylinder or a spare tank in rotation will prevent interruptions.
Seasonal cost is calculated at three sessions per week over 20 weeks, which reflects a typical spring-through-fall outdoor season in a moderate U.S. climate. Adjust your own estimate by changing hours per session and scaling sessions per tank to your actual usage pattern.
For fire tables with built-in fire pit propane tank enclosures, the enclosure is sized for a 20 lb cylinder. If the calculator shows fewer than two sessions per tank for your fire table's BTU rating, the only options are more frequent swaps, a separate 100 lb tank with a flex hose connection, or selecting a lower-BTU burner model.
A brief note on storage safety: NFPA 58, the Liquefied Petroleum Gas Code, requires that propane cylinders in use be stored upright and outdoors, with the cylinder valve in the closed position when the appliance is off.
Propane tank covers protect the valve and cylinder from weather while keeping it in an upright, code-compliant position. The NFPA 58 standard covers residential LP-gas use and is the governing document for cylinder storage across most U.S. jurisdictions.
Choosing Between a 20 lb and 100 lb Tank for Outdoor Fire Features
The 20 lb cylinder dominates the residential market because it is portable, available at hardware stores, and slots neatly into fire table enclosures. It is the right choice for occasional use (one to two sessions per week) or for appliances rated at 40,000 BTU or below.
The 100 lb cylinder reduces swap frequency by a factor of five. For households running a fire pit or fire table three or more evenings per week, the cost per gallon on a 100 lb refill is also typically lower than an exchange program on 20 lb tanks.
The 500 lb tank (or permanently plumbed natural gas line) is a consideration for commercial settings, restaurants with outdoor dining, or residential properties where outdoor fire pits are operated as a near-daily amenity.
Frequently Asked Questions
How do I calculate my propane usage?
Divide your appliance's BTU rating by 91,500 to find gallons burned per hour. Multiply that number by session length for gallons per session, then divide your tank capacity (4.7 gal for 20 lb, 23.6 gal for 100 lb) by that figure to find how many uses you get per fill.
How long will a 20 lb propane tank last at a 50,000 BTU fire pit?
A 20 lb tank holds 4.7 gallons, equivalent to roughly 430,050 BTU total. At 50,000 BTU per hour that provides approximately 8.6 hours of runtime at full output. Running the same fire pit at medium can stretch that to 14 to 17 hours spread over multiple evening sessions.
How many gallons of propane does a patio heater use per hour?
Patio heaters typically rate between 30,000 and 46,000 BTU per hour. At 40,000 BTU that equals approximately 0.44 gallons per hour. A standard 20 lb tank delivers around 10 to 12 hours at full output, though running at medium and spreading sessions can extend that further.
How long does a 100 lb propane tank last on a fire pit?
Running a 50,000 BTU fire pit burns roughly 0.55 gallons per hour. A 100 lb propane cylinder holds 23.6 gallons, providing about 43 hours of full-output runtime. Used three hours per evening, that covers approximately 14 backyard sessions before the tank needs a refill.
What size propane tank do I need for a gas fire table?
Fire tables typically rate between 40,000 and 90,000 BTU per hour. A 20 lb tank works for occasional sessions at lower output, while a 100 lb cylinder suits regular use or high-BTU models. Most fire table cabinet enclosures are sized to hold a single 20 lb cylinder.
Does running a propane fire pit on a lower setting reduce gas consumption?
Yes, most gas fire pits use a proportional valve, so a lower flame setting reduces BTU output and fuel consumption proportionally. A 60,000 BTU burner throttled to half output burns around 0.33 gallons per hour instead of 0.66, nearly doubling runtime on the same tank.
Final Thoughts
The propane calculator usage question almost always comes down to one decision: is a 20 lb tank enough, or is a 100 lb cylinder worth the switch? For most single-appliance backyard setups used two to three evenings per week, a 20 lb tank with one spare in rotation covers the season comfortably. The cost-per-session math rarely exceeds ten dollars at current propane rates, which is a fraction of the value delivered by a well-designed outdoor fire feature.
Where the calculator pays for itself most is in seasonal planning. Knowing you will burn 45 to 60 gallons over a 20-week season lets you time refills in advance rather than discovering an empty tank on a Friday evening. Enter your appliance's actual BTU rating for the most accurate estimate.
