Log moisture checker
The calculator needs JavaScript. The worked example, formula and figures below show exactly how it works, so you can do the sum yourself. A guide, not advice. Check the figures against your stove's manual, your supplier and your installer.
Short answer
Enter the readings from your moisture meter, taken on a freshly split face. The checker averages them and tells you whether your logs are at or below 20%, the Ready to Burn threshold, and flags readings that disagree. Every reading is editable, and the average can be passed straight into our firewood calculator.
Worked example
| You enter | Value |
|---|---|
| Meter readings | 17, 19, 21 % |
| Measured on a freshly split face | Yes |
| The log has been indoors at room temperature for a day | Yes |
Ready to burn: average 19.0%
- Within the guidance Average moisture: 19 % UK-wide: Ready to Burn: wood sold in small volumes at or below this moisture content (RtV). Check with the source.
| Result | Value |
|---|---|
| Your logs | Ready to burn |
| Average reading | 19% |
| Highest reading | 21% |
| Ready to Burn threshold | 20% |
Show the working
- Average: (17 + 19 + 21) ÷ 3 = 19%
- 19% is at or below 20%: ready
How it works
- Average = the sum of your readings ÷ the number of readings
- Ready when the average is at or below the Ready to Burn threshold (20%, source to be confirmed)
- Above it, keep seasoning and measure again in a few weeks
Measure properly: split a log from the middle of the stack, let it reach room temperature, and press the pins into the fresh face along the grain. Readings from the end grain or the outside read drier than the wood really is.
Pin meters differ: check your meter's manual for the wood setting and how it reports moisture.
Assumptions and sources
The figures this calculator starts from, and where each comes from. Your stove's spec plate, your supplier and your own meter readings come first: change any figure to match.
This calculator has no built-in defaults: every figure comes from you or your product's data.
| Table | Clause | Nations | Status |
|---|---|---|---|
| Rules by nation: smoke control, Ecodesign, fuel sales, CO alarms, Building Regulations gov.uk, gov.wales, gov.scot, nidirect, Defra, HETAS and Woodsure (Researcher to add each page) | Brief §0 and §3 rules.json. We explain and link the rules; we never say an appliance or fuel is legal in an area. | UK-wide | 1/22 values entered Not yet checked against the source |
Rules of thumb and reference figures are checked against their sources before launch; anything not yet checked is marked.
What to buy
A pin-type moisture meter reads in seconds. Choose one with a wood setting and replaceable pins.
FAQs
What moisture content should firewood be?
At or below 20%, measured on a freshly split face. That's the Ready to Burn threshold for wood sold in small volumes.
How many readings should I take?
At least three across the split face of each log, and more than one log from the batch. The checker averages them.
Why do my readings vary so much?
The outside and cut ends dry first, and cold wood can read wrongly. Bring the log indoors for a day, split it and measure along the grain. See log moisture content explained.
My logs are above 20%. What now?
Keep seasoning them: split, stacked off the ground, top covered, sides open. Measure again in a few weeks. See how to season firewood.
Guides
Best log moisture meters (UK): specs compared
Log moisture meters compared on makers' specs: pins, wood settings and range. Not tested. How to use one properly.
Log moisture content explained: dry enough?
What log moisture content means, why 20% matters, and how to measure it properly with a pin meter on a freshly split face.
Ready to Burn explained: the wood-fuel label
What the Ready to Burn label on logs means, the moisture rule behind it, and how to check your own logs with a meter.