Firewood Seasoning Time & Moisture Content Calculator

How it works

Months = species base (ash/pine 7, maple 10, oak 16) × split × stacking × climate factors; moisture (dry basis) = (wet − oven-dry) ÷ oven-dry; remaining ∝ ln(MC ÷ 20) ÷ ln(70 ÷ 20); heat lost ≈ water lb × 1,200 BTU

Freshly cut wood is half water or more, and every pound of that water costs about 1,200 BTU to boil off before the wood can burn — heat that also chills the fire, produces smoke and condenses as creosote in the flue. Seasoning to 20% moisture or below is therefore the single most important thing a wood burner controls, and it is governed by species (dense oak dries in two years what ash manages in one), by split size (moisture leaves through the end grain and cut faces), and by exposure to sun and wind with the rain kept off the top. Moisture meters read the fresh face of a split piece; the oven-dry weight method is the reference. Pin meters and firewood standards use the dry basis, so a meter's 20% corresponds to about 17% of the wet weight.

Worked example

Medium oak splits stacked well in a temperate climate need about 16 months from green; at 45% moisture now they have roughly 10 months to go. Burned today, about 6% of their energy would go into boiling off water — 4% less heat than seasoned wood on paper and far more in a smouldering fire — and three cords would need to shed about 2,250 lb (270 gallons) of water to reach 20%.

Frequently asked questions