Campfire Wood Calculator
Firewood weight, volume, and logs for any campfire evening.
What it does
Campfire wood runs out at the worst moment when guests guess by armload. Heat math is kinder: hours times fire size gives BTU, and BTU divided by wood energy gives weight. A medium evening lands near 15 pounds, not a truckload.
The tool above multiplies burn hours by a size preset, then converts to weight, stacked volume, and split count. Imperial mode reports pounds and cubic feet; metric mode reports kilograms and cubic meters. Both use seasoned hardwood near 20 % moisture.
Those constants come from federal energy and fire guides: a stacked cord is 128 cubic feet, and hardwood near 20 million BTU per cord. The Department of Energy publishes firewood heat values by species, and the Forest Service teaches the 4 x 4 x 8 foot cord in measurement guides.
Plan with dry wood in mind. Wet splits can need twice the stack for the same heat, and wind steals more. Bring the computed load plus a spare bundle, keep the fire modest, and put it fully out with water, stir, and a bare hand heat check.
How to use
- Pick imperial (lb, ft3) or metric (kg, m3).
- Enter burn hours for the evening.
- Pick fire size: small, medium, or large.
- Read wood weight, volume, and split count.
- Add one spare bundle for wind or late nights.
- Check bans and clear the ring before lighting.
Formula
- hours
- Burn time in hours.
- size
- Fire size: 15k small, 30k medium, 50k large BTU per hour.
- 7740
- BTU per pound of seasoned hardwood.
- 20M
- Cord energy used for volume: 20 million BTU.
Size presets are 15,000, 30,000, and 50,000 BTU per hour. A hardwood cord holds about 20 million BTU per 128 ft3 (3.625 m3). Log count divides weight by 3 lb (1.4 kg) per split. Wet or soft wood needs more than shown.
Worked example
Example: 4 hours, medium fire
4 hour medium campfire with seasoned hardwood.
- Burn is 4 hours at Medium (30,000 BTU per hour).
- Heat: 4 x 30,000 = 120,000 BTU.
- Weight: 120,000 / 7740 = 15.5 lb.
- Volume: 120,000 / 20,000,000 x 128 = 0.77 ft3.
- Logs: 15.5 / 3 = 5.2, so 5 split logs.
Reference table
| Evening | Heat | Wood |
|---|---|---|
| 2 hours | 60,000 BTU | 7.8 lb (3.5 kg) |
| 4 hours | 120,000 BTU | 15.5 lb (7.0 kg) |
| 6 hours | 180,000 BTU | 23.3 lb (10.5 kg) |
| 8 hours | 240,000 BTU | 31.0 lb (14.1 kg) |
| Large 4 hours | 200,000 BTU | 25.8 lb (11.7 kg) |
Limits
- Seasoned hardwood assumed. Wet or soft wood needs more.
- Presets are averages; wind and cooking shift real burn.
- Volume is stacked cord slice, not loose pile.
- Bans and site rules override any number.
Common mistakes
- Burning wet or painted wood.
- Planning exact logs with no spare.
- Leaving fires to mind themselves.
- Stacking fuel against the ring edge.
- Skipping the drown, stir, and feel check.
Try it yourself
Quick checks. Answers sit tucked under each question.
Wood for 6 hours large in metric?
Heat is 300,000 BTU. Weight is 300,000 x 0.000293071 / 5 = 17.6 kg. Volume is 0.054 m3. Logs are 13.
Wood for 6 hours medium in imperial?
Heat is 180,000 BTU. Weight is 180,000 / 7740 = 23.3 lb. Volume is 1.15 ft3. Logs are 8.
Questions
What do small, medium, and large mean?
Small near 15,000 BTU per hour (chat circle), medium near 30,000 (cook and warmth), large near 50,000 (group blaze). Wind and wet wood push real use above the pick.
How much heat does firewood hold?
About 7740 BTU per pound for seasoned hardwood near 20 % moisture. Softwood gives less per cord and burns faster. Wet wood wastes heat boiling water, so cover stacks and burn dry splits.
What is a cord of wood?
A full cord is 128 cubic feet stacked (4 x 4 x 8 ft) holding about 20 million BTU in hardwood. Campfires use a small slice: this 4 hour medium burn is 0.006 cord.
How heavy is one log?
Near 3 lb per split (1.4 kg) for a typical 16 inch hardwood split. Rounds and fat knots run heavier; kindling runs lighter. Count is weight divided by that average.
Does twice the time need twice the wood?
Yes, within the same heat. Double hours or step up a size and wood doubles. Halve the burn and it halves. That linearity is why the table scales cleanly.
What safety steps matter most?
Check fire bans, keep fires small in wind, clear 10 feet to bare soil, and drown, stir, and feel for heat. Never leave a fire alone and never burn trash or treated lumber.
Sources
- US Department of Energy: firewood heat
- US Forest Service: measuring firewood
- EPA Burn Wise: best wood burning practices