Is this firewood BTU calculator online free?

Yes. The calculator is free, requires no account, and processes the values you enter locally in your browser.

Free, instant & private

Firewood BTU Calculator Online

Q: How many BTUs are in a cord of firewood?

A full cord of air-dried firewood commonly contains about 14 million to 30 million BTU depending mainly on species and density. Air-dried white oak is about 25.7 million BTU per cord in the reference data used here.

Q: How much usable heat comes from a cord of wood?

Usable heat equals the wood's estimated energy multiplied by the appliance's overall efficiency. A 25.7 million BTU cord used in a 72% efficient stove would deliver roughly 18.5 million BTU under the calculator assumptions.

Q: Does wet firewood produce less heat?

Yes. Some of the fire's energy is used to heat and evaporate water, and wet wood can also burn poorly and create more smoke. The EPA recommends properly dried firewood with a moisture reading of 20% or less.

Q: Is a face cord the same as a full cord?

No. A full cord is 128 stacked cubic feet. This calculator treats a face cord as one-third of a full cord, assuming 16-inch log length; local definitions can vary.

See how much heat is hiding in your woodpile. Choose the species, stack size, moisture level and heater to estimate gross energy, usable room heat, kWh equivalent and heating time.

Your firewood

Start with your stack, then refine the result with real moisture and appliance efficiency.

Wood species

Stack amount

Stack unit

Moisture content

Test a freshly split face; 20% or less is seasoned.

Appliance

Overall efficiency

72%

Use overall efficiency, not the usually higher combustion efficiency.

Target heat output

BTU/hour

Used only to estimate how long the usable heat could last.

Your entries stay in this browser.

Estimated usable heat

18.5million BTU

25.7 million BTU gross energy before appliance losses

72% capturedoverall efficiency

Electric heat equivalent5,423 kWh

At your target output617 hours

Continuous heating time25.7 days

Standard cord equivalent1.00 cord

Seasoned wood, efficient burn. At 20% moisture, this white oak stack is in the recommended range for cleaner, hotter burning.

Planning estimate only. Real output varies with wood density, stack tightness, moisture measurement, rot, appliance condition, draft, burn rate, installation and operating technique.

How the firewood BTU calculator works

A cord is a volume, not a weight, so dense species generally pack more wood fibre—and more energy—into the same stack. This calculator starts with published heat-per-cord values for air-dried wood, adjusts for your stack volume and moisture, then applies the overall efficiency of your stove, insert, fireplace or boiler.

1. Size the stack

Enter full cords, face cords, stacked cubic feet or stacked cubic metres. One full cord is 128 stacked cubic feet.

2. Account for the burn

Moisture uses heat to evaporate water. Appliance efficiency estimates how much remaining energy actually reaches your space.

3. Compare useful output

See usable BTU, equivalent electric resistance heat, and hours of heat at your selected BTU-per-hour target.

The estimate: species BTU per cord × cord equivalent × moisture adjustment = gross available energy. Gross energy × overall appliance efficiency = usable room heat. The kWh comparison uses 3,412 BTU per kWh.

Firewood BTU per cord by species

These comparison values assume air-dried firewood at roughly 20% moisture. Individual trees, local growing conditions, decay, stacking and measurement methods can shift actual results.

Firewood species	Million BTU per full cord
Osage orange	30.7
Hickory	28.0
White oak	25.7
Red oak / sugar maple	24.0
White ash	23.6
Paper, gray or river birch	20.3
Red or silver maple	18.7
Quaking aspen	18.2
Pine, broad planning average	15.0

Dry wood matters. The U.S. EPA recommends firewood with a moisture reading of 20% or less. Wet wood can create more smoke, waste heat and increase creosote buildup. Never burn treated, painted, stained, rotten or toxic wood.

Cord, face cord and firewood stack conversions

A full cord is a neatly stacked pile measuring 128 cubic feet—commonly 8 feet long by 4 feet high by 4 feet deep. “Face cord” and “rick” are informal terms that vary by region. This online calculator uses the common assumption of 16-inch logs, making one face cord equal to one-third of a full cord. For the most reliable result, measure the stack’s length × height × depth and use stacked cubic feet or cubic metres.

1 full cord

128 stacked ft³, or about 3.62 stacked m³.

1 face cord / rick

About 42.7 stacked ft³ when logs are 16 inches long.

Loose vs. stacked volume

Loose-thrown wood contains more air space. Use the calculator only for neatly stacked measurements.

Firewood heating output FAQ

How many BTUs are in a cord of firewood?

A full cord of air-dried firewood commonly contains roughly 14 million to 30 million BTU, depending mostly on wood species and density. The calculator uses 25.7 million BTU for a cord of white oak at about 20% moisture.

How much usable heat comes from a cord of wood?

Multiply the cord’s estimated energy by the appliance’s overall efficiency. For example, 25.7 million BTU × 72% is about 18.5 million BTU of usable heat. Installation, draft and operation still affect actual output.

Does wet firewood produce less heat?

Yes. Energy is spent heating and evaporating water, while a cooler, smokier burn can further reduce useful output. Split a sample and test the freshly exposed face with a moisture meter; 20% or less is the recommended target.

Is a face cord the same as a full cord?

No. A full cord is 128 stacked cubic feet. A face cord is one row of logs, commonly 4 feet high by 8 feet long. Its depth depends on log length, so this calculator’s one-third-cord conversion assumes 16-inch logs.

What efficiency should I use for a wood stove?

Use the overall efficiency listed for your exact model when possible. Overall efficiency represents heat transferred to the heated space and is more useful here than combustion efficiency. Presets are broad planning values, not ratings for a specific appliance.

Is this online firewood BTU calculator free and private?

Yes. It is free to use without signing up, and the numbers you enter are processed locally in your browser.

Reference data: U.S. Forest Service Forest Products Laboratory guidance on basic wood energy, Penn State Extension’s heating with wood species table, and U.S. EPA guidance on wood-heater efficiency and moisture.