Campfire BTU Calculator

This calculator works backward from a target heat output to the pounds and bundles of firewood needed, accounting for how little of a campfire's energy actually becomes useful heat. Target Heat Output and Burn Duration are both pure multipliers of the total useful BTU the fire must deliver, so a 10% increase in either one raises Wood Needed and Estimated Wood Cost by the same roughly 20% swing -- neither one outweighs the other. Wood Type has the single largest real effect on Wood Needed of any input, even larger than either of those two: switching from Hardwood (about 8,500 BTU per pound, the default) to Softwood (about 7,000 BTU/lb) raises Wood Needed by roughly 21%, since more of the lower-energy wood is needed to hit the same target, while switching to Kiln-Dried (about 9,500 BTU/lb) lowers it by roughly 11%.

Fire Efficiency starts at a flat 12% (typical for an open campfire, where most heat escapes upward rather than warming the area around it) and only shifts at temperature extremes -- it drops to 10% below 32°F and rises to 13% above 80°F, with no change in between. Because Ambient Temperature's effect only appears once it crosses one of those two thresholds, a small adjustment near the default 55°F leaves Fire Efficiency, and therefore Wood Needed, completely unchanged. This is a rough planning estimate -- real firewood energy content varies by species and moisture content, and wind, fire size, and reflector setups all change actual campfire efficiency.