Douglas Fir vs. Grand Fir (Firewood BTU Test)

On a standard, dry-cord basis, Douglas fir usually has a small heat advantage over grand fir. Reference tables commonly estimate about 20–21 million Btu per cord for Douglas fir and 19–20 million for grand fir. These are estimates, not guaranteed test results. Moisture, stacked volume, piece size, and stove operation can matter more than the species difference.

A moisture meter and a consistent way to measure your wood make this comparison far more useful than a species label alone. I treat a BTU table as a starting point, then check the split face, the stack, and the firewood actually going into the stove. That approach helps avoid two common losses: burning wet wood and spending time hauling wood that yields less heat per load.

One recent improvement in firewood practice is the routine use of handheld moisture meters. They do not replace good seasoning or a sound stack, but they can help you check a batch instead of guessing from bark, weight, or calendar time. For a fair species comparison, use them on both firs in the same way.

Douglas fir vs. grand fir heat per cord

Douglas fir and grand fir are both useful firewood, but reference tables generally give Douglas fir a modest advantage per standard cord. The figures below are estimates for dry wood, not results from one controlled stove test. Compare equal stacked volumes at similar moisture before deciding which pile will heat your home better.

These figures are useful for planning, not precise predictions. Published values can differ with the source, the wood’s moisture, and the way a cord is measured. Density helps explain the trend: a cord of denser wood can hold more wood mass in the same stacked space. But density and heat tables do not tell you exactly how much usable heat your stove will deliver.

A standard cord is 128 cubic feet of stacked wood, including the air spaces between pieces. A loose pile, a pickup load, or a stack with unusually large gaps is not an equal cord. If you compare by eye, the volume difference can outweigh the modest gap between the two firs.

Takeaway: Douglas fir is usually the stronger choice for heat per measured dry cord, but the gap is small enough that moisture and stack volume deserve equal attention.

What a fair firewood BTU comparison measures

A fair comparison holds the main conditions steady: equal solid-wood volume, similar moisture content, comparable piece size, and similar storage and stove use. “Solid-wood volume” means the wood itself, not the air gaps in a stack. Without these controls, a comparison may reflect how the wood was measured or dried more than its species.

For a home test, keep Douglas fir and grand fir separate. Cut them to similar lengths, split them to roughly similar sizes, and stack each in a clearly measured space. Note the species, splitting date, storage conditions, and moisture readings. If you burn the wood to compare performance, keep the stove’s settings and loading approach as consistent as practical.

Do not compare green Douglas fir with dry grand fir and call the result a species test. Wet wood has to use heat to warm and evaporate water, so it may deliver less useful heat and can contribute to smoke and creosote problems. A species name cannot correct for poor seasoning.

Takeaway: A controlled comparison starts with equal, measured loads at similar moisture, not with a quick burn of whatever is closest to the stove.

Moisture content and drying checks

Moisture content, or MC, describes how much water remains in wood. For firewood, aim for about 20% MC or less, checked on a freshly split interior face with a suitable meter. The meter reading is one check, not a promise that every piece in the stack is equally dry.

To test a piece, split it shortly before measuring and press the meter’s pins into the fresh face as the meter instructions direct. Take readings from several pieces in each stack, including pieces from different parts of the pile. Avoid relying on a reading from bark or an old exposed surface, which may not represent the inside of the wood.

Check what moisture scale your meter uses. Wood moisture can be reported on a dry basis or a wet basis; the numbers are not interchangeable. Many consumer firewood meters report dry-basis MC, but confirm the manual rather than assuming. Use the same meter and method for both species so the readings are comparable.

There is no reliable universal drying time for either fir. Seasoning depends on starting moisture, split size, airflow, sun, rain exposure, and stacking. Splitting rounds sooner and stacking off the ground with open sides can support drying, but only repeated checks can tell you when a particular batch is ready.

Takeaway: Use a fresh split face, several samples, and a consistent meter method. Target 20% MC or less rather than relying on a fixed number of months.

Field comparison: two practical scenarios

These scenarios show how to interpret the wood you have; they are not controlled test results. I use comparisons like these to separate a species advantage from a seasoning or measurement problem. The key question is whether the loads are truly comparable before drawing a conclusion about heat.

In a yard comparison, the most useful record is often simple: species, stack dimensions, split size, date, and several meter readings. I would not report a small difference in burn time as proof that one species has a fixed BTU advantage. Stove draft, air control, load size, and how the pieces are arranged can all change the result.

Takeaway: Treat a home burn as a practical check, not a laboratory test. Keep the inputs alike and record what you changed.

Equipment setup and safety preparation

A chainsaw setup is model-specific, not species-specific. Douglas fir and grand fir do not call for a universal bar length, chain type, fuel mix, or tuning value. Use the saw maker’s approved bar and chain combination, its specified fuel, and its instructions for adjustment and operation.

Before cutting, wear a helmet, eye and face protection, hearing protection, chainsaw-rated leg protection, gloves, and protective footwear. Check your footing, escape path, bystanders, overhead hazards, and the stability of each log. Follow applicable local rules; OSHA requirements apply to covered logging work, and ANSI Z133 practices are relevant where applicable.

Inspect the chain, brake, throttle interlock, chain catcher, and bar lubrication system. Confirm chain tension and lubrication as the saw manual directs. Use the manufacturer-specified fuel mix; 50:1 is correct only when the manual specifies it. Bar length and chain pitch, gauge, and drive-link count must match the saw and bar.

Takeaway: Match the saw to its manual before cutting. No generic setup is safe or correct for every model.

Field cutting and firewood comparison

Bucking means cutting a log into firewood lengths. Secure each log against rolling, work from a stable position, and keep the bar nose clear of unintended contact. Rotational kickback can occur if the upper quadrant near the bar nose strikes wood, throwing the saw rapidly toward you.

Keep a firm two-handed grip and do not cut above shoulder height. Avoid an unstable stance or a blocked escape path. Do not force a binding cut; stop and change the setup. When measuring wood for comparison, keep each species in its own stack and record the dimensions so loose piles are not mistaken for equal cords.

Takeaway: Cut safely first; then measure each species as a separate, comparable stack.

Maintenance, chain sharpening, and saw tuning

A sharp chain cuts more cleanly and helps you avoid forcing the saw. Knots, dirt, and dry bark can dull or damage a chain, even though both firs are softwoods. If cutting slows or the saw produces fine dust instead of the expected chips, stop and inspect the chain rather than pushing harder.

Sharpen the chain and set depth gauges to the saw and chain makers’ specifications. There is no single correct raker clearance for every chain. Follow the manual for chain tension, bar-oil type and flow, and idle and full-throttle speed. Do not use generic RPM or oil settings in place of model-specific directions.

Takeaway: Stop when the chain is dull or damaged. Correct it to the maker’s specifications before continuing.

Storage and seasonal care

Storage protects the saw and preserves the firewood comparison. After cutting, switch off the saw and let it cool in a clear area. Clean the air filter, bar groove, oil holes, sprocket area, and chain according to the manual; store fuel and the saw as the maker directs.

For firewood, keep stacks stable and raised off the ground, with room for air to move. Protect the top from rain while leaving sides open where practical. Store the two firs separately and label them with species and cutting or stacking dates. Recheck moisture before burning rather than assuming the same drying schedule works every year.

Takeaway: Keep clean, labeled stacks and verify moisture before loading the stove.

Conclusion: which fir should you choose?

Douglas fir generally offers slightly more heat per standard dry cord than grand fir, based on commonly cited reference estimates. That does not make grand fir poor firewood. If it is dry, well stacked, and already on hand, it can serve well. For either species, moisture near or below 20%, measured volume, and safe processing are central to a useful comparison.

If you are choosing what to stack first, prioritize wood that is already cut and can season well, then compare dry, equal volumes. Record meter readings and stack size. That gives you a more dependable answer for your own woodlot than a BTU figure alone.

Takeaway: Expect a modest per-cord edge for Douglas fir, but make the decision with dry, measured wood and safe, consistent handling.

Frequently asked questions

Does Douglas fir give more heat than grand fir?
Usually, per standard dry cord. Reference estimates commonly place Douglas fir around 20–21 million Btu and grand fir around 19–20 million Btu. These are ranges, not guaranteed results.

Which fir is better firewood?
Douglas fir generally has a small heat-per-cord advantage. Either can be useful if properly seasoned and burned in a suitable appliance.

How dry should Douglas fir and grand fir be?
Aim for about 20% MC or less. Measure a freshly split interior surface with a suitable meter and follow its instructions.

Can I compare a green cord with a dry cord?
No. Differences in water content can overwhelm the small estimated heat gap between the species.

How many Btu are in a cord of Douglas fir?
Common reference estimates are about 20–21 million Btu per standard cord. Actual usable heat depends on moisture, measurement, and burning conditions.

How many Btu are in a cord of grand fir?
Common reference estimates are about 19–20 million Btu per standard cord. Treat this as an estimate, not a fixed result.

What counts as a standard cord?
A standard cord is 128 cubic feet of stacked wood, including air gaps. Loose piles are not directly comparable to a cord.

How long do these firs take to season?
There is no dependable fixed timeline. Split size, airflow, weather, starting moisture, and storage affect drying, so use meter checks.

Can a moisture meter read through bark?
Do not rely on a bark reading. Split a sample and measure the fresh interior face according to the meter instructions.

Does either fir need a special chainsaw chain?
Not because of species alone. Use the chain type and bar combination approved for your saw, and maintain it to the maker’s specifications.

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