How to Check Firewood Moisture Correctly

Split a log and test the freshly exposed inner face with a wood moisture meter, sample several logs and use the readings to separate ready wood from wood that needs drying

A two-pin wood moisture meter held against the freshly split inner face of a firewood log

Measure the moisture inside the log

Split a sample log
Expose a fresh inner face rather than testing the dry outside
Take a meter reading
Follow the meter’s wood settings, pin direction, contact depth and temperature guidance
Check several logs
Sample different parts of the stack before judging the whole supply

EPA guidance uses less than 20% moisture as the target for firewood ready to burn

Measure inside the log, not just the dry outside

A log may feel dry on the surface while retaining moisture inside · Bark, an old exposed split face and the end of a log can give a misleading picture of the interior · Use a fresh split to expose the material you need to test

Check the meter
Select its wood mode, fit a sound battery and use any supplied calibration check as the manual describes
Choose a representative log
Include the larger pieces you actually intend to burn, not only thin kindling from the front of the stack
Split it safely
Support the log securely and keep hands clear of the splitting operation · Set the newly split piece down before taking a reading
Test the fresh inner face
Make firm contact near the middle of the split surface, away from bark, ends and visible metal · Use the manufacturer’s pin orientation and insertion instructions
Take more than one reading
Check a few positions on that face and record the readings before moving to another log

EPA’s moisture-meter leaflet recommends testing a newly split surface and checking multiple places · Follow your own instrument’s manual where its measurement method differs · A pinless meter may require a flat contact area, a particular thickness and a species setting that are awkward to achieve on an irregular log

Sample different parts of the wood stack

For a practical household check, start with at least three logs taken from different locations, including a less exposed part of the stack · This is a useful sampling routine, not a certification that every piece in a delivery is dry · Test more pieces if results differ widely, the load contains mixed sizes or you are about to rely on a whole batch

Record the stack or delivery, the date, the meter setting and the range of readings for each log · Mark separate batches so a ready stack does not become mixed with newly delivered wood

Worked example	Fresh-face readings	Useful next action
Log A	17%, 18%, 18%	Readings are below the target threshold
Log B	22%, 24%, 23%	Keep this batch drying and sample nearby logs
Log C	19%, 20%, 20%	Check the meter conditions and allow more drying if borderline

The example is illustrative data, not a Firesided test · Averaging the whole table into one attractive number would hide the wetter log · Use the results to decide which wood to separate, dry longer or investigate

What moisture reading is ready to burn?

Use the appliance manufacturer’s fuel instructions alongside the moisture reading · EPA’s firewood guidance recommends less than 20% · A displayed value close to the threshold is not an exact laboratory measurement, particularly if the meter’s accuracy or correction settings are uncertain

A low reading does not establish that wood is otherwise suitable fuel · Do not use it to justify burning painted, coated, glued or preservative-treated material · Keep fuel selection separate from the question of moisture

Check doubtful readings before making a decision

Possible problem	What to check
Cold or frozen logs	Use the operating-temperature range and correction method in the meter manual · Temperature can change resistance readings
Wrong measurement mode	A masonry or relative scale is not a wood moisture percentage
Only bark or end grain tested	Split another representative log and test its fresh inner face
Readings change with every attempt	Check battery, pin contact, surface condition and the meter’s calibration check
Numbers above the meter’s range	Treat them as a sign the wood needs further assessment or drying, not a precise high-moisture measurement

Delmhorst explains that temperature affects resistance-type wood moisture measurements and provides correction guidance · The correction depends on the instrument and conditions · Do not apply a number found for a different meter without checking compatibility

The meter’s manual should also explain whether species correction is needed · A sound-looking stack, checking at the log ends or a hollow sound when pieces are knocked together can help you select samples, but those observations do not replace a fresh-face measurement

Dry the wetter wood and retest it

Keep the stack off the ground, protect it from rain and leave a path for moving air · Avoid enclosing wet logs tightly on every side · Separate incoming wood from the stack you have already checked, and label the delivery date

Retest representative logs before moving a batch into regular use · A calendar estimate alone cannot account for log size, wood species, weather and storage conditions · See how to store firewood outside for the storage arrangement

Once you know which wood is ready, use the firewood consumption calculator to plan stock · Use the firewood storage-size guide to compare stacked volume with usable storage space · Moisture percentage and cubic volume answer different questions