Sarah stared at the enormous pile of logs dumped on her driveway last October, feeling a mix of excitement and dread. The wood dealer had promised her “enough for the whole winter,” but standing there in her wellies, she couldn’t shake the feeling she’d either bought way too much or nowhere near enough.
Three months later, with January’s bitter winds howling outside, Sarah found herself rationing logs and eyeing the thermostat nervously. She’d become another casualty in the great firewood guessing game that trips up thousands of homeowners every year.
Getting your cubic metres firewood calculation right isn’t just about comfort—it’s about avoiding the panic of running out mid-February or the frustration of overspending on wood that’ll still be rotting in your garden come spring.
Why Getting Your Firewood Math Right Actually Matters
As energy costs continue climbing and more households turn to wood heating, calculating the right amount of firewood has become crucial. Wood burning can slash heating bills and provide independence from volatile gas prices, but only if you buy smart.
The challenge lies in understanding that firewood isn’t sold like other fuels. Unlike filling your car with petrol, where you know exactly what you’re getting, firewood comes in confusing measurements that vary wildly between suppliers.
“Most people have no idea what they’re actually buying when they order firewood,” says timber merchant James Mitchell, who’s been supplying logs for over 20 years. “They hear ‘cubic metre’ and think they understand, but the reality is far more complex.”
A “stère”—the traditional French measurement—officially means one cubic metre of logs cut to one-metre lengths and neatly stacked. But here’s where it gets tricky: most modern wood burners can’t handle metre-long logs.
When suppliers cut those logs down to 50cm, 33cm, or 25cm pieces, something interesting happens. The shorter pieces stack more tightly together, so your cubic metre of wood suddenly occupies less space. You’ve got the same amount of actual wood, but it might only fill 0.7 to 0.8 cubic metres when stacked.
The Factors That Determine Your Firewood Needs
Working out how many cubic metres firewood you need isn’t a one-size-fits-all calculation. Several key factors dramatically affect consumption:
- Home size and ceiling height – A 60m² bungalow needs far less than a 180m² farmhouse with high ceilings
- Insulation quality – Modern well-insulated homes use roughly half the wood of older properties
- How often you heat – Primary heating versus occasional evening fires makes a huge difference
- Local climate – Northern regions and exposed locations increase consumption significantly
- Wood burner efficiency – Modern stoves extract far more heat from each log than old open fireplaces
“A typical modern, well-insulated home between 90-110 square metres using wood as primary heat usually needs 5-7 cubic metres of good hardwood per year,” explains heating engineer Lisa Thompson. “But that can easily double for older properties with poor insulation.”
| Home Type | Size (m²) | Annual Firewood Need (m³) |
|---|---|---|
| Modern apartment | 50-70 | 3-4 |
| Well-insulated house | 90-120 | 5-7 |
| Older house (good condition) | 90-120 | 8-10 |
| Period property | 120-180 | 10-15 |
| Large rural home | 180+ | 15-20 |
The Hidden Costs of Getting It Wrong
Miscalculating your firewood needs hits your wallet in multiple ways. Order too little, and you’ll pay premium prices for emergency deliveries in January when demand peaks and quality drops. Many suppliers add hefty delivery charges for small orders, sometimes doubling the cost per cubic metre.
Order too much, and you’re stuck with wood that degrades over time. Properly seasoned logs left outside for more than two seasons start losing their heating efficiency. Worse, inadequate storage leads to rot, insect infestations, and wood that smokes heavily when burned.
The quality issue becomes critical during peak winter months. “By February, most suppliers are scraping the bottom of the barrel,” warns wood supplier Mark Peters. “The good, well-seasoned stuff goes early. People who didn’t plan ahead often end up burning wood with 25-30% moisture content instead of the ideal 15-20%.”
High-moisture wood produces less heat, creates more creosote buildup in chimneys, and generates more emissions. You’ll burn more logs for the same warmth while potentially violating clean air regulations in smoke control areas.
Smart Strategies for Accurate Planning
The key to nailing your cubic metres firewood calculation lies in honest assessment and careful planning. Start by tracking your usage patterns if you’ve burned wood before. Keep a simple log of how many wheelbarrows or armloads you use daily during cold periods.
For newcomers to wood heating, err on the side of caution but don’t go overboard. Start with the middle range for your home type and adjust next year based on actual experience.
Consider your heating strategy too. Using wood as primary heat source means continuous burning throughout cold months. Supplementary heating for evenings and weekends dramatically reduces consumption.
“Most first-time buyers underestimate storage requirements,” notes forestry expert Dr. Helen Crawford. “You need dry, ventilated space for your entire season’s supply, plus room to season next year’s wood properly.”
Quality matters more than quantity. Well-seasoned hardwood with 15-20% moisture content burns hotter and longer than cheaper, wetter alternatives. You’ll need fewer cubic metres of premium wood than bargain logs that hiss and struggle to ignite.
FAQs
How do I know if wood is properly seasoned?
Good firewood has visible cracks in the ends, feels lighter than green wood, and makes a sharp crack when two pieces are knocked together. Avoid wood that feels heavy or looks freshly cut.
Should I buy wood by weight or volume?
Always buy by volume (cubic metres) rather than weight. Wet, unseasoned wood weighs more but provides less heat, making weight-based pricing misleading.
Can I reduce the amount I need by mixing wood with other fuels?
Yes, many people use wood for evening and weekend heating while relying on gas or electric for background warmth. This can cut firewood needs by 50-70%.
When’s the best time to buy firewood?
Order in spring or early summer for the following winter. Prices are lower, quality is better, and you’ll have time to properly store and further season the wood.
What’s the difference between hardwood and softwood for heating?
Hardwoods like oak, ash, and beech burn longer and hotter, requiring fewer cubic metres for the same heat output. Softwoods ignite easier but burn faster.
How long does properly stored firewood last?
Well-seasoned hardwood stored in dry, ventilated conditions maintains quality for 2-3 years. After that, it starts losing density and heating value.
