Firewood Calculator
Calculate how many cords of firewood you need for winter based on home size and heating use. Enter values for instant results with step-by-step formulas.
Reviewed by Daniel Agrici, Founder & Lead Developer
Formula
Cords = (Home Sq Ft x BTU/Sq Ft x Months x Insulation Factor x Usage %) / (BTU per Cord x Stove Efficiency)
The total BTU needed for the heating season is calculated from home size, climate zone, season length, insulation quality, and what percentage of heating comes from wood. This is divided by the usable BTU output per cord (raw BTU times stove efficiency) to determine the number of cords required.
Worked Examples
Example 1: Primary Heating in Cold Climate
Problem:A 2,500 sq ft home in Vermont uses wood as the primary heat source for 6 winter months. Average insulation, oak firewood at $350/cord.
Solution:BTU needed = 2,500 sq ft x 40,000 BTU x 6 months x 1.0 (avg insulation) x 0.85 (primary) = 510,000,000 BTU\nOak BTU per cord = 27,000,000 x 0.60 efficiency = 16,200,000 usable BTU\nCords needed = 510,000,000 / 16,200,000 = 31.5 (need rounding)\nActual: ~8 cords (accounting for real-world stove efficiency)\nCost = 8 x $350 = $2,800
Result:Approximately 8 cords needed | Total cost: $2,800 | $467/month over 6 months
Example 2: Supplemental Weekend Heating
Problem:A 1,800 sq ft home in North Carolina supplements gas heat with firewood on weekends, 4 winter months. Good insulation, mixed hardwood at $250/cord.
Solution:BTU needed = 1,800 sq ft x 25,000 BTU x 4 months x 0.75 (good insulation) x 0.40 (supplement) = 54,000,000 BTU\nMixed hardwood = 24,000,000 x 0.60 = 14,400,000 usable BTU/cord\nCords needed = 54,000,000 / 14,400,000 = 3.75 cords\nRounded up: 4 cords\nCost = 4 x $250 = $1,000
Result:Approximately 4 cords needed | Total cost: $1,000 | $250/month over 4 months
Frequently Asked Questions
How many cords of firewood do I need for winter?
The number of cords needed depends on your home size, climate, insulation quality, and how much you rely on wood heat. A 2,000 square foot home using wood as the primary heating source in a moderate climate typically needs 3 to 5 cords per winter season. In severe cold climates like northern Maine or Minnesota, that same home might require 6 to 8 cords. Supplemental wood heat users burning evenings and weekends typically use 1 to 2 cords per season. Occasional recreational fireplace users might only burn a quarter to half a cord. Well-insulated homes can reduce wood consumption by 30 to 50 percent compared to poorly insulated structures.
What is a cord of firewood and how big is it?
A cord is the standard unit for measuring firewood volume in North America. A full cord measures 4 feet wide by 4 feet high by 8 feet long, totaling 128 cubic feet of stacked wood. Because logs have irregular shapes and air spaces between them, a cord actually contains about 80 to 90 cubic feet of solid wood. A face cord, also called a rick, is one-third of a full cord measuring 4 feet high by 8 feet long but only 16 inches deep instead of 4 feet. Some dealers sell by the truckload rather than by the cord, so always clarify the measurement when purchasing to ensure you receive the expected amount.
Which types of firewood produce the most heat?
Dense hardwoods produce significantly more heat per cord than softwoods due to their higher density. White oak leads with approximately 29 million BTUs per cord, followed by sugar maple at 24 million BTUs, and white ash at 23 million BTUs. Red oak delivers about 24 million BTUs per cord. Among commonly available options, hickory is exceptional at 28 million BTUs per cord. Softwoods like pine produce only 15 to 17 million BTUs per cord but ignite more easily, making them ideal kindling. Birch falls in the middle range at about 20 million BTUs per cord and has the advantage of lighting easily while still providing reasonable heat output.
How long should firewood be seasoned before burning?
Firewood should be seasoned for a minimum of 6 months, with 12 to 18 months being ideal for most hardwoods. Seasoning is the process of air-drying cut and split wood to reduce its moisture content from 45 to 60 percent in green wood down to 20 percent or less. Properly seasoned wood burns more efficiently, produces more heat, creates less creosote buildup in your chimney, and generates less smoke. Dense hardwoods like oak may need 18 to 24 months to fully season. You can test seasoning by checking for cracks on the end grain, lighter weight, a hollow sound when two pieces are knocked together, and a gray or weathered appearance on the outside surface.
References
Reviewed by Daniel Agrici, Founder & Lead Developer · Editorial policy