What Is Red Fir’s Heat Value? (Cord BTU Chart)

Red fir firewood is commonly listed at about 20.6 million BTU per full cord. That figure is a comparison value, not a promise of heat from every load: moisture, the amount of solid wood in the stack, and correct species identification all matter. A full cord is 128 cubic feet of stacked wood, including the air spaces between pieces.

A dry, neatly stacked pile can look like a solid block of fuel. A wet, loosely stacked pile may look just as large, yet give you less useful heat. The BTU number helps compare wood, but it only makes sense when you know what the chart counts and how the wood was measured.

Red fir’s heat value and cord BTU chart

Red fir’s commonly cited heat value is about 20.6 million BTU per full cord. A BTU, or British thermal unit, is a measure of heat energy. Treat the chart value as an estimate for comparison, not as the heat your home or stove is guaranteed to receive.

*The smaller amounts are simple proportions of the commonly cited full-cord value. They assume the same species, dryness, and stacking method. They do not predict delivered heat from wet, mixed, or loosely measured wood.

The full-cord figure is useful when comparing firewood listings. It is not an appliance output rating. A stove’s actual heat output depends on factors such as the appliance, how it is operated, and the fuel’s condition. Published wood charts may also differ because their sources use different assumptions, including different moisture levels.

What “per cord” means

A full cord is a stack measuring 4 feet high, 4 feet deep, and 8 feet long. Those dimensions equal 128 cubic feet of stacked space. The space includes both wood and gaps between the pieces; it does not mean 128 cubic feet of solid wood.

This distinction matters when buying firewood. A pile that looks large may not contain a full cord if it is short, shallow, loosely stacked, or measured in a different way. Ask how the seller measures the load, and check the stack’s dimensions when possible. “Face cord” and similar local terms can refer to different amounts, so they are not a reliable substitute for a stated full-cord volume.

How to interpret the red fir BTU number

The 20.6-million-BTU figure is best read as a standard chart estimate for a full cord of identified red fir. It gives you a way to compare wood types on paper. It does not account for every real-world difference in moisture, piece size, stacking, or burning conditions.

Moisture changes usable heat

Moisture content is the amount of water held in the wood. Freshly cut or wet wood must lose water as it burns. That uses energy that could otherwise help heat the room, and wet fuel may also burn poorly in an appliance.

For firewood, aim to season the wood to about 20% moisture content or less. Check a freshly split face with a moisture meter, following the meter’s instructions. Testing only the outside of a log can give a misleading result because the surface may be drier than the center.

The chart value should not be treated as guaranteed heat from green or rain-soaked wood. It is also not possible to calculate an exact delivered-heat figure from moisture alone without more information about the wood and appliance.

Species names can be confusing

“Red fir” generally means California red fir, Abies magnifica. Common names vary by region, however, and firewood may be sold under local or informal names. Do not assume a seller’s “red fir” is the same as Douglas-fir or another fir species.

If the species is uncertain, ask for the botanical or local identification and compare it with a trusted regional reference. A BTU chart cannot identify a log by appearance alone. It also cannot tell you the chain, bar, or engine settings needed to cut it.

Red fir identification, cord measurement, and equipment safety

Before you rely on a heat-value estimate, confirm what wood you have and how much is stacked. If you prepare it yourself, use equipment only as its maker directs. A firewood BTU rating describes fuel energy; it is not a chainsaw or appliance specification.

Red fir is a wood species, while a chainsaw is a tool used to cut wood. Fuel mix, chain pitch and gauge, chain sharpening, raker setting, bar-oil flow, and engine speed depend on the saw model. Use the manufacturer’s manual for those details rather than trying to infer them from a cord BTU chart.

For cutting work, wear chainsaw-rated leg protection, a helmet with eye and face protection, hearing protection, gloves, and suitable boots. Check your footing, overhead hazards, escape routes, and the location of bystanders before starting. Follow the saw maker’s safety instructions and the rules that apply where you work; professional forestry work may also be subject to standards such as ANSI Z133 and OSHA 29 CFR 1910.266.

A bent or loaded log can split suddenly as it is cut. This is sometimes called a barber-chair failure: the stem can split lengthwise and rise with great force. Assess supports and tension before cutting, stay clear of the likely split path, and do not attempt a cut if you cannot manage the wood’s movement safely. A qualified professional is the safer choice for a hazardous or heavily stressed stem.

Preparing, cutting, and seasoning red fir firewood

Seasoning means drying split wood before burning it. The aim is to reduce moisture, not simply to leave rounds in a pile for a set number of months. Drying time varies with conditions, so check the wood rather than relying only on a calendar.

A practical preparation sequence is:

• Confirm the wood and amount. Identify the species as well as you can, and measure the stack using the full-cord dimensions if you are buying or tracking volume.
• Split large rounds. Smaller pieces expose more surface area and can dry more readily than whole rounds. Choose piece sizes that suit your appliance.
• Stack for airflow. Keep the wood off the soil and allow air to move around the stack. Cover the top to limit rain, but leave the sides open.
• Check before burning. Split a piece and measure the moisture on the fresh face. Aim for about 20% or less, using the meter as its maker directs.
• Cut with control. Use a maintained saw and a chain matched to that saw. Support the log to reduce pinching, consider where it is under tension or compression, and keep the bar nose clear of contact that could cause kickback.

Do not cut above shoulder height, bypass safety features, or force a dull chain through wood. These actions can increase the risk of losing control or suffering kickback. If a log is unstable or its stresses are unclear, stop and get qualified help.

Firewood storage, moisture checks, and appliance care

Storage protects the work you put into drying wood. Keep seasoned firewood from sitting on wet soil, and cover the top against rain while leaving the sides open to moving air. Before burning, confirm dryness and use only an appliance approved for cordwood.

A useful check is to split a representative piece and test its newly exposed face. If readings vary across the stack, do not assume the driest piece represents all the wood. Moisture can differ among pieces and within a piece, so take more than one reading when you need a clearer picture.

Burn red fir only in an appliance designed and approved for cordwood, and follow that appliance’s operating instructions. A BTU-per-cord chart does not tell you how much wood to load or how to control a stove. Follow the maker’s guidance for those choices.

Remove ash only when it is safely cool. Inspect and clean the appliance and flue on the schedule set by the manufacturer and local fire-safety guidance. Dry fuel and careful operation are useful, but neither replaces routine maintenance.

Common questions about red fir heat value

These short answers clarify how to use the chart without treating an estimate as a guarantee. The key figures are about 20.6 million BTU per full cord and 128 cubic feet of stacked space; moisture and species identification affect how well those figures apply.

How many BTU are in a cord of red fir?
A commonly cited chart value is about 20.6 million BTU per full cord.

How many cubic feet are in a full cord?
A full cord is 128 cubic feet of stacked wood, including the gaps between pieces.

Is 20.6 million BTU guaranteed heat from my stove?
No. It is a fuel comparison estimate, not a guaranteed appliance output. Moisture, the measured amount of wood, and appliance operation all matter.

Does red fir mean Douglas-fir?
Not necessarily. Red fir generally refers to California red fir, Abies magnifica. Common names vary, so confirm the species rather than assuming they are interchangeable.

How dry should red fir be before burning?
Aim for about 20% moisture content or less. Check a freshly split face with a meter and follow its instructions.

Can I use the chart value for freshly cut red fir?
Use caution. The chart figure is not a guaranteed value for wet or freshly cut wood. Wet wood can provide less useful heat in practice.

How much energy does a half cord represent?
A simple proportional estimate is about 10.3 million BTU, assuming the same wood, dryness, and stacking conditions as the full-cord figure.

Does the BTU chart tell me what chainsaw chain to use?
No. Chain pitch, gauge, sharpening, and other saw settings are model-specific. Use the chainsaw manufacturer’s instructions.

The practical takeaway is simple: use 20.6 million BTU as a reference for a full cord of red fir, then check the species, stack volume, and moisture before relying on the estimate.

(This article was written by one of our staff writers, Evan Bradley. Visit our Meet the Team page.)