Firewood Calculator (Cords, Volume & Cost)

Firewood Guide

What's the key thing to understand about Firewood Units Explained?

Firewood is sold in a confusing variety of units, which makes comparing prices hard. A cord is the traditional measure (common in North America): a stacked pile measuring 4 × 4 × 8 feet, equal to 128 cubic feet or about 3.62 cubic metres of stacked wood (including the air gaps between logs). A face cord (or 'rick') is one-third of a full cord — a stack 4 feet high and 8 feet long but only one log deep, so its volume depends on the log length. In the UK, firewood is more often sold by the cubic metre, by bulk bag (typically around 0.6-0.85 m³, often quoted as 'roughly 1 cubic metre' loosely), by the load (van or trailer load — an imprecise measure), or by net/dumpy bags. Loose-thrown versus stacked: a 'loose cubic metre' of thrown logs contains less actual wood than a 'stacked cubic metre' because of larger air gaps — typically about 0.7 m³ of wood per loose m³. This is a common source of confusion and apparent overcharging. When comparing prices, always try to compare the same unit (ideally stacked cubic metres or weight of seasoned wood) and ask whether a quoted volume is loose or stacked.

What's the difference between Seasoned and Wet Wood?

The single most important factor in firewood quality is moisture content. Freshly cut ('green') wood can be 50%+ water by weight. Burning wet wood is inefficient and harmful: much of the heat is wasted boiling off water rather than warming your home, it produces more smoke and creosote (which builds up in chimneys and is a fire risk), and it pollutes more. Seasoned or kiln-dried wood should be below 20% moisture (ideally 15-20%). It lights easily, burns hot and clean, and produces far more usable heat per log. In the UK, the 'Ready to Burn' certification scheme indicates wood sold at 20% moisture or less — and since 2021, regulations restrict the sale of wet wood in small volumes for exactly these reasons. Seasoning: freshly cut wood typically needs 1-2 years of air-drying (split, stacked off the ground, covered on top but open at the sides for airflow) to season properly. Hardwoods take longer than softwoods. Kiln-dried wood is dried artificially and ready immediately, at a premium price. A moisture meter (cheap and widely available) lets you check wood before burning — under 20% is the target.

How Much You'll Need?

Annual firewood needs vary enormously with how you burn. As a rough guide: occasional use (a fire on cold evenings, not for primary heat) might use 1-3 cubic metres a season. Regular use (most evenings through the heating season) might use 3-7 cubic metres. Primary heat source (heating the home mainly with wood) can use 7-15+ cubic metres a season, depending on home size, insulation, stove efficiency, and climate. Factors that affect consumption: stove efficiency (a modern, well-rated stove extracts far more heat per log than an open fire, which is very inefficient — much heat goes up the chimney), home insulation, how cold your winters are, and how much of your heating the wood provides. Wood species matters too: dense hardwoods (oak, ash, beech, hornbeam) burn longer and hotter per log than softwoods (pine, spruce), though softwoods light easily and are fine for kindling and quick fires. This calculator estimates how long a given volume will last at your burn rate, or how much to buy for a season — useful for budgeting and for buying in bulk (which is usually cheaper) rather than expensive small bags.

What's the key thing to understand about Buying and Storing?

Buying smartly and storing well saves money and ensures good burning. Buying: bulk is cheaper per unit than small bags, so if you have storage, buying a larger quantity (and ideally seasoning it yourself, or buying seasoned in bulk) cuts cost. Compare prices on the same basis (stacked m³ or weight of seasoned wood). Buy 'Ready to Burn' certified or check moisture yourself. Beware vague units like 'a load' — ask for the volume. Storing: keep wood off the ground (on pallets or rails) to prevent it drawing up damp. Cover the top to keep rain off, but leave the sides open for airflow — wood needs ventilation to stay dry and to continue seasoning. Store in a sunny, breezy spot if seasoning. Bring a few days' supply indoors before burning so it's at room temperature and any surface moisture dries. Stack stably. Safety and regulations: in the UK, Smoke Control Areas restrict what you can burn and require approved ('exempt') appliances — check whether you're in one. Only burn dry, seasoned wood (never treated or painted wood, which releases toxic fumes). Sweep your chimney regularly (at least annually for regular use) to prevent dangerous creosote build-up. This calculator helps with quantities and cost; for installation and safety, follow stove manufacturer guidance and local regulations.

Which Wood Species Burn Hottest and Longest?

Firewood is broadly divided into hardwoods and softwoods, and the difference in density between species has a direct effect on heat output and burn duration for a given volume of wood. Hardwoods — oak, ash, beech, hawthorn and fruit woods like apple and cherry — are generally denser than softwoods, which means a given volume contains more burnable material, producing more heat output and a longer, slower burn per log, making them the preferred choice for sustained heat in a wood burner or open fire. Ash is particularly well regarded among UK hardwoods for burning well even at a slightly higher moisture content than most species tolerate, and for producing a clean, steady flame, while oak burns very slowly and densely but benefits from a longer seasoning period than most other hardwoods before it's ready to burn well. Softwoods — pine, spruce, larch — are less dense, burn faster and hotter initially but for a shorter duration, and tend to produce more resin and spit more while burning, along with creating more creosote build-up in a chimney or flue over time if used as a primary, regular fuel rather than for kindling or occasional use. Birch sits somewhat between the two categories, burning reasonably hot and reasonably long despite technically being a hardwood with lower density than oak or ash, and is popular partly because it seasons relatively quickly compared with slower-seasoning hardwoods like oak. For sustained winter heating, a mix weighted toward denser hardwoods generally gives better value and performance than relying mainly on fast-burning softwoods.

What Moisture Content Should Firewood Reach Before Burning?

Firewood moisture content has a major effect on how efficiently and cleanly it burns, and burning wood before it's properly seasoned is one of the most common reasons people get poor heat output, excessive smoke, and rapid creosote build-up from a wood-burning stove or open fire. Freshly cut ("green") wood can have a moisture content of 45-50% or higher, and burning wood at this moisture level wastes a significant proportion of the fire's energy simply evaporating that trapped water before any useful heat is produced, which is why green wood burns poorly, smokes heavily, and produces far less usable heat than the same wood once properly seasoned. Well-seasoned firewood ready for efficient burning should generally have a moisture content below 20%, and ideally closer to 15-18% for the best combustion efficiency and cleanest burn — this is also now a regulatory consideration in the UK, where wood sold for domestic burning in smoke control areas and for use in most modern stoves must meet "Ready to Burn" certification standards specifying a moisture content below 20%. A simple, inexpensive moisture meter — pressed into a freshly split face of a log rather than the weathered outer surface, which reads inaccurately dry — gives a reliable measurement and is a worthwhile investment for anyone regularly burning their own seasoned wood rather than buying pre-certified kiln-dried logs. Properly seasoned wood is also noticeably lighter than green wood of the same size, and well-seasoned logs typically show visible cracking or splitting at the cut ends and often have a slightly duller bark colour compared with freshly cut wood.

Worked Example: Heating a Typical Home Through One Winter

A household using a wood burner as a secondary heat source, lit most evenings through a typical heating season (roughly October to March, about 150 heating days), burning an average of 8kg of seasoned hardwood logs an evening, needs approximately 150 x 8 = 1,200kg of wood for the season. Seasoned hardwood like oak or ash has a density of roughly 650-750 kg per cubic metre of stacked, loosely packed logs (a "cord" measure varies by region, but a UK-style "loose m3" of logs is the common retail unit), so 1,200kg works out to roughly 1,200 / 700 = 1.7 cubic metres of stacked logs, typically sold as two or three standard builder's bags or a comparable loose-tipped load. Buying wet, unseasoned wood instead of kiln-dried or properly seasoned (under 20% moisture) stock can cut usable heat output by 20-30%, because a meaningful share of the fire's energy goes into boiling off trapped moisture rather than heating the room — meaning the same household burning wet wood might need to buy closer to 1.5-1.6 cubic metres more than this estimate just to get the same warmth, on top of producing more smoke, tar and creosote buildup in the flue.