Firewood Drying Time Calculator

How this is calculated

THE FIGURES HERE COME FROM THE EPA'S BURN WISE PROGRAMME, and that matters because almost everything else written about seasoning firewood disagrees with itself. Published times for the same species range from six months to three years, because they quietly fold in split size, stacking, cover and climate without saying which they assumed. The EPA gives two numbers and states the conditions they apply under: 'Split, stack, cover and store your firewood for six months if it is a softwood, and at least one year for hardwoods.' THE CLOCK STARTS WHEN THE WOOD IS SPLIT, NOT WHEN THE TREE CAME DOWN. That is why the split checkbox resets the count here rather than shortening it. A round log dries through the bark, which is the part of the tree evolved specifically to stop moisture leaving - a log left whole for a year can be barely drier than the day it was cut. Splitting opens the end grain and the face, and the EPA period is written as time after splitting and stacking. ⚠️ THE MOISTURE METER IS THE TEST, AND THE CALENDAR IS ONLY THE PLAN. The EPA is explicit: 'Wood burns best at a moisture content of less than 20 percent. Test wood with a wood moisture meter before you burn it.' Months elapsed is a way to know roughly when to start checking. It is not a substitute for checking. Wood stacked badly can sit for two years and still be wet; wood split small and stacked in wind and sun can beat the baseline. Split a piece and meter the FRESH inside face - the outside of any stack reads dry after a sunny afternoon and tells you nothing. STORE IT OFF THE GROUND WITH ONLY THE TOP COVERED. The EPA wording is 'Store wood outdoors, off the ground, with only the top covered -- covering the sides traps in moisture.' A tarp wrapped over the whole stack is the single most common mistake, and it is worse than no tarp at all: rain is kept off, but so is the airflow that does the actual drying, and the wood ends up sweating inside a plastic tent. Ground contact does the same thing from below, wicking moisture straight back into the bottom course. ⚠️ BURNING WET WOOD IS A SAFETY PROBLEM, NOT JUST AN INEFFICIENT ONE. Water in the wood has to be boiled off before the wood itself can burn, so a wet fire runs cool and smoky. Unburnt smoke condenses in a cold flue as creosote, and creosote is what chimney fires are made of. The heat you lose is the mild half of the problem. This is why the tool will not tell you the wood is ready - it tells you when to start testing, and the meter tells you the rest. THE STORAGE CONDITIONS ARE COUNTED, NOT PENALISED. If you have not met all three, the tool says so and does not silently add months, because the EPA does not publish a figure for how much longer badly stored wood takes and this calculator will not invent one. Treat a count below three as a reason to distrust the calendar entirely and go straight to the meter. HARDWOOD TAKES TWICE AS LONG BECAUSE IT IS DENSER. The same volume holds more wood and more water, and the water has further to travel out. That density is also why it is worth the wait - it is the reason a hardwood fire burns longer from the same stack space.

Common questions

How long does firewood really take to season?

The EPA's Burn Wise programme gives six months for softwood and at least one year for hardwood, measured from the point the wood is split, stacked, covered on top and kept off the ground. Those are the numbers this calculator runs on, and they are worth trusting over most of what is written elsewhere - published seasoning times for the same species range from six months to three years, because they fold in split size, stacking, cover and climate without stating which they assumed. The EPA figures are useful precisely because they come with their conditions attached.

Does the clock start when the tree was cut or when the wood was split?

When it was split, which is why this tool resets the count if you untick the split box. Bark is the part of a tree specifically evolved to stop moisture escaping, so a round log dries mainly through its two cut ends and can sit for a year barely drier than the day it came down. Splitting opens the end grain and exposes the face, and the EPA period is written as time after splitting and stacking. If you have a pile of rounds that has been sitting for two years, treat the seasoning as starting the day you split them.

Why does the tool refuse to say my wood is ready?

Because months elapsed cannot tell you that, and the one thing that can is cheap. The EPA's instruction is to test with a moisture meter and burn below 20 percent. Wood stacked against a fence with a tarp over the sides can sit for two years and still be wet; wood split small and stacked in wind and sun can beat the baseline comfortably. The calendar tells you roughly when to start checking. Reaching zero months here is a prompt to go and measure, not a verdict.

Where on the log should I take the meter reading?

On a freshly split face, across the grain, near the middle of the piece. The outside of any stack reads dry after a sunny afternoon and tells you nothing about the inside, which is where the remaining water is. Take a piece from the middle of the stack rather than the end, split it, and meter the new face straight away. If you get very different readings from different pieces, that is real - a stack does not dry evenly - and the wet ones are the ones that decide whether you should be burning it.

Should I cover the whole stack with a tarp?

No, and this is the most common mistake in the whole subject. The EPA wording is to store wood outdoors, off the ground, with only the top covered, because covering the sides traps moisture in. A tarp wrapped over an entire stack keeps rain off but also stops the airflow that does the actual drying, and the wood ends up sweating inside a plastic tent. It is genuinely worse than leaving the stack open to the weather. Cover the top, leave the sides and ends open, and if you can, point the long side of the stack at the prevailing wind.

What actually goes wrong if I burn it wet?

The water in the wood has to be boiled off before the wood itself can burn, so a wet fire runs cool and smoky and gives you noticeably less heat from the same stack. That is the mild half. The serious half is that unburnt smoke condenses in a cool flue as creosote, and creosote is the fuel in a chimney fire. It is also why a wet fire is dirtier for everyone downwind. Burning below 20 percent moisture is a safety practice first and an efficiency one second.

My storage conditions count is below three - how many extra months should I add?

This tool will not tell you, deliberately. The EPA publishes the seasoning times and the conditions they assume, but no figure for how much longer badly stored wood takes - and inventing a multiplier here would be exactly the kind of confident-sounding guess that makes the rest of the writing on this subject useless. What a count below three should do is change your approach: stop treating the calendar as meaningful for that stack and go straight to the meter. Then fix whatever is missing, because it costs nothing and the next stack will not have the same problem.

The margin figure is negative. What now?

It means this stack will not have reached the baseline by the time you said you need it, so plan around that rather than hoping. Buy properly seasoned wood for the coming season and let this batch become next year's - which is the position most people who burn wood end up in permanently, working a year ahead. If you are close rather than far off, splitting the pieces smaller and moving the stack somewhere windier and sunnier genuinely helps, and costs an afternoon. What does not help is burning it anyway and telling yourself it is nearly there.

Take it further with AI

Copy this into ChatGPT or Claude with your own numbers filled in. It hands over the figures this calculator worked out, so the answer is built on real arithmetic instead of a guess.

I used the Firewood Drying Time Calculator at https://www.bfcbrilliance.com/tools/firewood-drying-time-calculator.

What I entered:
- Wood type: ___
- Months since it was split and stacked (months): ___
- Months until you need to burn it (months): ___
- It is split, not left in rounds: ___
- Stacked off the ground: ___
- Top covered, sides left open: ___
- Moisture meter reading (%): ___

What it calculated:
- Months left on the EPA clock: ___
- How far through the baseline: ___
- Margin before you need it: ___
- Storage conditions met, of 3: ___
- Points above the 20% target: ___

Use those figures as given — they are already worked out, so please don't recalculate or estimate your own. Help me turn them into a plan: what to buy or do, in what order, roughly what it should cost, and the mistakes people most often make with this job.

More firewood tools