Enter log weight, wood type, and moisture to predict hourly burn and heat output fast. Save fuel, keep plants warm, and track loads easily.
| Wood type | Moisture (%) | Load (kg) | Efficiency (%) | Airflow (%) | Wind (m/s) | Target time (h) | Burn rate (kg/h) | Heat output (kW) |
|---|---|---|---|---|---|---|---|---|
| Oak (hardwood) | 20 | 8 | 70 | 100 | 2 | 3 | 2.74 | 8.10 |
| Pine (softwood) | 30 | 6 | 65 | 110 | 4 | 2.5 | 3.24 | 7.16 |
| Mixed/unknown | 15 | 10 | 75 | 90 | 1 | 5 | 1.68 | 6.12 |
Example outputs are illustrative and depend on local conditions and equipment.
Moisture content controls how much energy becomes plant‑warming heat. Wet fuel spends energy heating and evaporating water, so the same log mass produces fewer usable megajoules. For garden heaters, aim for seasoned wood around 15–25% moisture to stabilize output and reduce smoke. If your meter reads above 30%, expect a burn rate to maintain the same heat.
Hardwoods usually carry higher energy per kilogram and pack more mass per volume than many softwoods. That matters when you store wood near beds or a greenhouse, because dense species can deliver longer burns per stack. Softwoods can still be useful for quick warm‑ups, but they often require more frequent feeding. Keep stacks off soil, cover the top, and allow side airflow to prevent re‑wetting.
Air control is the simplest lever for changing burn rate. More airflow raises combustion speed and heat output, but shortens burn time. Wind acts like extra draft, especially for open pits, increasing consumption and temperature swings. Use windbreaks, sheltered placement, and steady air settings for predictable results. If gusts rise, reduce airflow.
When target heat is unknown, a quick demand estimate uses area, heat‑loss coefficient, and inside‑outside temperature difference. This supports decisions such as whether one heater is enough or if supplemental insulation is needed. Compare estimated kilowatts to calculated output and look for a safety margin during frost alerts. Tighten doors, seal gaps, and use thermal curtains to lower demand without burning extra wood.
Burn rate converts directly to daily wood needs, which helps schedule cutting, drying, and refills. Add a price per kilogram to translate performance into hourly operating cost and to compare wood against other heat sources. Record inputs and outcomes across several nights, then adjust moisture assumptions, load size, and airflow to match your microclimate. Consistent logs and repeatable settings are the fastest path to stable overnight protection more reliably.
Burn rate is the estimated wood mass consumed per hour after moisture, efficiency, setup type, airflow, and wind effects are applied. It helps you plan how often to refill and how much wood to stage for a cold night.
Split a log and use a moisture meter on the fresh inner face. Take several readings and average them. If you cannot measure, assume 25% for seasoned wood and 35–45% for freshly cut wood.
Wind increases oxygen delivery and pulls hot gases away, acting like extra draft. Open fires are most sensitive. Using a windbreak and reducing airflow can stabilize output and extend burn time.
Use target burn time when you know how long a load must last, such as overnight protection. Use target heat output when you have a heat goal, such as maintaining a greenhouse temperature, and you can refill as needed.
Lower heat loss first: seal leaks, add insulation, and use thermal curtains. Then use drier wood and a controlled setup. Small airflow reductions often cut consumption while keeping a steady, useful heat output.
They are typical reference values for dry wood and will vary by species, bark, seasoning, and storage. The calculator is best for planning and comparisons; calibrate it by logging real burn times and adjusting moisture or efficiency.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.