Firewood calculator: cords, ricks and face cords

How much is a cord of wood?

A full cord is split wood stacked 4 feet high, 4 feet deep and 8 feet long. That is 128 cubic feet, and it counts the air between the pieces as well as the wood.

The stack has to be neat and tight. A loose pile of the same size holds more air and less wood. A full-size pickup with an 8-foot bed holds about one third to one half of a cord.

Rick of wood vs. face cord vs. cord

A face cord has the same 4 foot by 8 foot face as a full cord, but it is only one piece deep. You may also hear it called a rick. Pieces are often 12 to 18 inches long, so the amount of wood in one changes with the piece length.

With 16-inch pieces, a rick is one third of a full cord. With 12-inch pieces it is a quarter of a cord, and with 24-inch pieces it is half.

How the firewood calculator works

To measure a stack, it does this:

For a winter's wood, it swaps one fuel for another by heat. Wood for wood: cords times the old wood's heat per cord, divided by the new wood's heat per cord. Another fuel for wood: the amount times its Btu per gallon or kilowatt-hour, divided by the wood's heat per cord.

If you enter both efficiencies, it also multiplies by your furnace's efficiency and divides by your stove's. That matches the heat that reached your rooms, not just the heat in the fuel.

What it assumes

• The stack is tight and even, the way a cord is measured.
• Heat per cord is the Utah State University Extension figure for each wood. Real wood varies with how dry it is.
• A wood for wood swap assumes the same stove, burned the same way.
• Fuel figures are the EIA's standard heat content for each fuel.

A Bonners Ferry example

Say your wood is stacked along the side of a shop outside Bonners Ferry. The stack is 24 feet long and 5 feet high, one row of 16-inch pieces.

Now say you burned 4 cords of lodgepole pine last winter, and this year you have larch (tamarack). 4 x 21.1 / 21.8 = 3.87, so about 3.9 cords of larch hold the same heat.

How much firewood do I need for winter?

It depends on your house, your stove and the winter. Your own use last year is the surest guide, and the calculator's "Wood for a winter" setting works from that.

If you burned wood, enter last winter's cords and the wood you have now. If you heated with propane, heating oil or electricity, enter what your bills or delivery slips show. The calculator turns it into cords that hold the same heat.

Firewood BTU chart: heat by wood type

When two woods are equally dry, the heavier one holds more heat. Here are a dozen woods from Utah State University Extension's firewood table.

Larch, lodgepole pine, birch and Douglas-fir sit at the top of this list. Ponderosa pine, cottonwood, Engelmann spruce and white fir give about 20 to 30 percent less heat per cord than Douglas-fir.

How long to season firewood

Season wood for at least six months, EPA says, and burn it at under 20 percent moisture. Illinois Extension says six to nine months, and to split logs more than 10 inches across so they dry.

Store it outdoors, off the ground, with only the top covered. Covering the sides traps moisture. A wood moisture meter tells you when it is ready. Wet wood gives less heat, because some of the heat goes into boiling off the water.

Cutting your own: permits

To cut firewood on the national forest, you need a permit from the U.S. Forest Service first.