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Generator Fuel Runtime Calculator

Estimate how long a generator will run on a tank of fuel at a given load.

Computed in your browser — nothing you enter is uploaded. Figures are presented for United States against IRC 2024, and every formula is cited under regulatory standards below.

Last verified 2026-08-25 · v1.0.0

Market
Imperial · sales tax

Estimated runtime

6.67 hours

Check your inputs

Actual runtime varies with load percentage, fuel type, temperature, and altitude — check your specific generator's published fuel consumption chart at your actual expected load for a more precise figure.

For the dimensions entered, expect a estimated runtime of 6.67 hours. Note that fuel tank capacity and fuel consumption rate (gal/hr) sit at the edge of the range this calculator was checked against, so treat the output as indicative rather than settled. Moderate confidence — sound arithmetic, but allow for the variation any real site introduces. Set for United States against IRC 2024. The market selector changes both the units and the code cited.

Preliminary estimate, not certified engineering. This tool produces an indicative quantity calculation for planning purposes only — it is not a certified structural analysis, a guaranteed material takeoff, or a substitute for building department approval. Always verify measurements on-site and have a licensed contractor or structural engineer review any load-bearing, code-sensitive, or safety-critical work before purchasing materials or starting construction. Spotted an arithmetic or standards error? Report it to contact@craftquantities.com with your inputs — confirmed fixes become pinned regression tests.

[Schema Verified] Computed in alignment with American Concrete Institute (ACI 318-19) formulas and International Residential Code (IRC 2024) spatial boundaries.

Regulatory standards & verification citations

  • Runtime (hours) = fuel tank capacity (gallons) / fuel consumption rate (gallons per hour) at the expected load

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Frequently asked questions

Why does load percentage affect fuel consumption so much?
An engine burns noticeably more fuel per hour the harder it works — running a generator near its full rated capacity can use significantly more fuel per hour than running it at half load, even though it's the same generator.
Should I run a generator at 100% load for best fuel efficiency?
No — running continuously at 100% load stresses the generator and shortens its lifespan. Most manufacturers recommend sizing a generator so your typical load sits comfortably below its maximum rating (see the Generator Sizing Calculator), not running it at its limit for extended periods.
Does this apply to natural gas or large propane tank standby generators?
The same runtime-per-fuel-volume math applies, but standby generators connected to a home's natural gas line effectively have unlimited runtime, and a large propane tank's capacity (often in hundreds of gallons) should be used instead of a small portable tank size.