How Many Cords of Firewood Do I Need for Winter?

The honest answer is "somewhere between 2 and 8 cords", and the right number depends on how cold your winters are, how big and tight your house is, what kind of stove you burn in, and how much of your heat comes from wood. Here is how to estimate it for your own house, so that you buy early, and neither run out in February nor pay for wood you do not burn.

What is a cord?

A full cord is a stack of firewood 4 ft high, 4 ft deep and 8 ft long: 128 cubic feet, including the air between the logs. A "face cord" (or rick) is 4 ft high and 8 ft long but only one log deep, so its size depends on the length of the logs: with 16 inch logs it is a third of a cord. "Truckload" is not a unit of measure. When you buy, ask for the dimensions, and measure the stack with the firewood cord calculator.

How the estimate works

1. How much heat does the house need? Roughly 15 thousand BTU per square foot per year in a mild climate, 30 in a moderate one, 45 in a cold one and 60 in a very cold one, adjusted up or down for insulation.
2. How much will wood supply? If the stove is your only heat, all of it. If it is a supplement to a furnace, maybe half.
3. How much heat is in a cord? That depends on the species (from about 16 million BTU for pine to 27 million for hickory) and on your stove, since only the fraction that is not lost up the chimney heats the house.

The firewood for winter calculator does this for your own house and stove.

Cords for 100% wood heat

With an EPA-certified stove (70% efficient), red oak (24 million BTU per cord) and average insulation. If wood supplies half your heat, halve the numbers.

Wood species matter

For a 2,000 ft² house in a cold climate heated entirely by an EPA stove, the same heat takes:

Softwoods are not worse wood: they light easily and burn hot, and are fine for shoulder seasons. But you need half again as much of them as you would of a dense hardwood to get the same heat, and they burn through faster.

Your stove matters even more

The same house, climate and wood (red oak), heated entirely by wood:

An open fireplace is a source of atmosphere, not heat: most of the heat it makes goes up the chimney, and it can even pull warm air out of the house. A modern stove or insert uses a fraction of the wood.

Buying and seasoning

• Buy early. Order in spring or summer, when prices are lowest and wood has time to dry. Cut or bought "green" wood needs 6 to 12 months (longer for oak) to season.
• Check the moisture. Well-seasoned firewood is below 20% moisture. A cheap meter tells you. Wet wood wastes heat boiling off water, smokes, and builds up creosote in the chimney.
• Stack it right. Off the ground, in a single row or a loose stack with gaps for air, in the wind and sun, with a cover on the top only.
• Measure what you buy. Stack the delivery and measure it. A dishonest "cord" is often 10 to 30% short.
• Keep extra. Winters vary: a 10 to 20% buffer saves a panicked February.

Keep the chimney safe

• Have the chimney and flue inspected and swept every year, before the season starts.
• Install smoke and carbon monoxide alarms near the stove and in the bedrooms.
• Keep a safe clearance from combustibles, use a hearth pad, and store ashes in a metal bucket outdoors.