Firewood Flex tool

Firewood calculator

How many Mega Bags, Boxes, or cords do you need? Tell us how often you light a fire, how long it burns, and what kind of fire it is. We do the math.

Fires per week

3 per week

Hours per fire

3 hours

Heating season length

Use case

Your season estimate

0 cu ft

0 cords

In Firewood Flex products

0 Mega Bags (1.75 cu ft each)
0 Boxes (1.33 cu ft each)
0 1/4 Cord pallets
0 1/2 Cord pallets

Estimated cost: $0 (using lowest-cost format)

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How we calculate the numbers

The math uses three inputs you can adjust above (fires per week, hours per fire, season length) and burn-rate constants drawn from public research.

Burn rates by use case (lb of dry hardwood per hour)

Use case	Rate	Source
Fireplace ambience (open hearth)	1.5 lb/hr	EPA Burn Wise residential wood-heater data, low draft setting
Primary heat (EPA wood stove)	4.0 lb/hr	EPA Wood Heater Test Report median, 25,000 BTU/hr output
Outdoor fire pit (open-air)	2.5 lb/hr	USDA Forest Service open-burn studies, exposed-air radiative loss
Pizza oven (Ooni / Gozney class)	2 lb per cook	Ooni Karu and Gozney Roccbox user-manual fuel guidance for a 60 to 90 min session at 700 to 950 degrees F
BBQ smoker (offset, kamado)	1.0 lb/hr	Texas A&M AgriLife Extension low-and-slow benchmark at 225 to 275 degrees F

Conversion constants

Cord: 128 cu ft of stacked wood (4 x 4 x 8 ft). Legal US weights-and-measures standard.
Dry hardwood weight: 3,900 lb per cord (averaged from USDA Forest Products Lab density tables for oak, ash, maple, cherry, birch at 12% moisture content).
Cubic feet per pound: 1 lb ≈ 0.033 cu ft (derived from cord weight).
Mega Bag: 1.75 cu ft (Firewood Flex spec, packed).
Premium Box: 1.33 cu ft.

What the calculator does NOT account for

This is a planning estimate, not a guarantee. Real-world fuel use varies based on:

Wood species and moisture: oak burns slower than ash. Kiln-dried (under 15% moisture) delivers 95% rated BTU, seasoned (20 to 25%) only 75 to 80%. See BTU chart.
Climate and insulation: a wood stove in Vermont vs Maryland same household can vary 2x in seasonal cord need.
Fire technique: top-down lighting, log placement, damper management all affect burn rate by 15 to 30%.
Appliance efficiency: open fireplace is 5 to 15% efficient. EPA-certified wood stove is 65 to 80%.
Local quarantine rules: if you live in a USDA APHIS quarantine zone (PA, NJ, NY, MA, MD), only kiln-dried USDA-certified wood is legal to transport.

Add 10 to 15% to the result for buffer. Results assume kiln-dried hardwood under 15% moisture (our spec). For higher-moisture cordwood, multiply by 1.3.

Sources

US EPA, Burn Wise residential wood heater performance database
USDA Forest Products Laboratory, Wood Density at 12% Moisture Content tables
Utah State University Cooperative Extension, Heating with Wood (publication HG/Wood/2008-01)
Texas A&M AgriLife Extension, Wood Selection for BBQ Smoke
National Conference on Weights and Measures (NCWM), Cord definition statute
Internal Firewood Flex kiln data, batches Q1 2025 to Q1 2026

Disclaimer

This calculator is a planning aid, not a guarantee of fuel quantity. Heating outcomes depend on your fireplace or stove efficiency, home insulation, regional climate, draft conditions, and fire-tending technique. Always store at least 10 to 15% more firewood than the calculator suggests. Firewood Flex Manufacturing LLC is not responsible for under or over-purchase decisions made from this tool. Numbers shown round up to the next whole bag, box, or pallet.