Coal/Gas Consumption Calculator

This calculator estimates how much fuel a forge session burns and what it costs, using a simple two-factor model: a base consumption rate per fuel type (8 lbs/hr for coal, 1.5 gal/hr for propane, 100 cu ft/hr for natural gas) scaled by a forge-size multiplier — 0.5× for a small single-burner setup, 1.0× for a medium 2-burner forge, and 1.5× for a large 3+ burner unit. Multiplying that hourly rate by your session length gives total fuel used, and multiplying total fuel by a per-unit cost (built in at $0.15/lb coal, $3.50/gal propane, $0.012/cu ft natural gas) gives an estimated cost. It also reports total BTU output by multiplying fuel consumed against a fixed energy density for each fuel — roughly 12,000 BTU/lb for coal, 91,500 BTU/gal for propane, and 1,030 BTU/cu ft for natural gas — so you can compare heat output across fuel types on equal footing.

Treat the numbers as planning estimates rather than a precise fuel gauge: real forges vary a lot by burner design, tip size, regulator pressure, insulation (fire brick vs. cast refractory), and how often the door or damper is left open, all of which this model collapses into a single size multiplier. Coal forges especially depend heavily on coal grade and how tightly the fire is banked between heats. Use this to budget propane tank refills or coal orders for a session or event, and to sanity-check whether switching fuel types is worth it cost-wise for your typical session length — but always keep a safety margin on tank/fuel supply rather than cutting it exactly to the estimate, since real consumption tends to run higher during extended high-heat work like welding or heavy stock removal.