Kiln Schedule FinderDrying Time and Temperature Schedule
Find the recommended kiln drying schedule for your species and thickness. Estimates total drying time, temperature steps, humidity targets and the risk of defects for a safe, efficient dry.
Why this calculation matters
The schedule decides drying time and degrade together. Too fast collapses cells and case-hardens the surface, and neither is recoverable.
Kiln Schedule Finder
Drying Time and Temperature Schedule
Sets drying severity class.
Drying time rises with thickness squared.
| Step | MC Range | Dry-Bulb | Wet-Bulb | Target EMC |
|---|
About Kiln Schedule Finder
A kiln schedule is a step-by-step plan of temperature and humidity that gradually removes moisture from wood without causing checking, honeycomb, collapse or case-hardening. Dense, refractory species like Teak and Oak need gentle schedules; permeable softwoods can be dried fast. This tool estimates total drying time and the temperature/humidity steps based on species, thickness and target MC. Instead of hunting for a drying schedule chart for your species, enter thickness and starting moisture and get a workable kiln drying time and temperature plan.
Where Is This Used?
Formulas Used
Drying time ~ k x Thickness^2 x severity_factor x ln(MC1/MC2)Thicker boards: time scales roughly with the square of thicknessSchedule steps decrease wet-bulb (raise temp) as MC dropsTarget EMC at each step is set ~2-4% below current wood MCKiln type factor: Vacuum ~0.3x, Conventional 1.0x, Solar ~1.8x timeHow the calculation works
Two things dominate: how thick the boards are, and how far they have to dry. Thickness matters far more than it looks, because moisture has to travel further and the path resistance grows with it. The last few points of moisture take longer than the first twenty.
Show the formula
Days = 0.55 x (thickness in cm)^1.7 x severity factor x ln(start MC / target MC) x kiln factor. The natural log reflects that drying slows as moisture falls; the thickness exponent reflects that time rises faster than thickness.An indicative duration, NOT a schedule. The thickness exponent has a physical basis: moisture movement is diffusion-limited, so drying time scales close to the square of thickness, and real drying falls a little below that because surface evaporation shares the resistance. The exponent of 1.7 sits inside that band. The severity and kiln-type multipliers are fitted to typical practice and have no published source. For the actual temperature and humidity steps use the FPL Dry Kiln Operator’s Manual, which publishes schedules by species and thickness.
References and what each one provides
- USDA FPL — Dry Kiln Operator’s Manual (AH-188)The standard reference for kiln schedules by species and thickness, and for the drying defects that govern how fast a charge can safely be taken down.Published kiln schedules by species and thickness, and the defects that limit drying rate.
- USDA Wood Handbook (FPL GTR-190)USDA Forest Products LaboratorySpecies drying behaviour and moisture movement.
Unverified values are marked as such rather than presented as sourced.
Limitations of this calculation
Suggests a schedule for the species and thickness entered. It does not account for kiln condition, airflow uniformity, stacking quality, initial moisture variation within a charge, or existing drying stress in the timber.
Do not use this for Production kiln control, or any schedule applied without operator supervision.
Figures are engineering estimates from the inputs and assumptions shown. Verify against the actual material and, where the result affects structure or safety, against a qualified professional.
- Thickness and MC-drop dependence of drying time
Formula checked against the sources above by an automated regression test (tests/verify-phase2.js) that derives each expected value independently of this page. Last reviewed .
How to use this tool
- Enter your wood and climate details below, then press Calculate.
- Pick your drying severity class and kiln type from the dropdown.
- Fill in board thickness, starting mc, target final mc.
- Press Calculate.
Worked example
Common mistakes to avoid
- Running a fast softwood schedule on thick hardwood. Oak and beech check and honeycomb if pushed.
- Trusting the schedule without kiln sample boards. Real charges vary; samples tell you the truth.
- Skipping conditioning at the end. Un-equalised lumber case-hardens and pinches saws later.
Frequently Asked Questions
Wood species data
Density, hardness and movement for 60 timbers
Full listing in the thermal conductivity reference.