43 Formulas
Wood Science Formulas
Moisture, shrinkage, density and kiln-drying equations.
VPD Calculator
VPD Calculator
SVP = 0.6108 x exp( (17.27 x T) / (T + 237.3) ) T in deg C, result kPaUsed in VPD Calculator
Green Weight Calculator
Green Weight Calculator
Green weight = Oven-dry mass x (1 + Green_MC/100)Used in Green Weight Calculator
Green Weight Calculator
Water to remove = Weight_current - Weight_targetUsed in Green Weight Calculator
Green Weight Calculator
Basic density = oven-dry mass / green volume (kg/m3)Used in Green Weight Calculator
Moisture Tracking Tool
Moisture Tracking Tool
MC% = (Wet weight - Oven-dry weight) / Oven-dry weight x 100Used in Moisture Tracking Tool
Moisture Tracking Tool
Drying rate = (Previous MC - Current MC) / Days elapsedUsed in Moisture Tracking Tool
Moisture Tracking Tool
Days to target = (Current MC - Target MC) / Drying rateUsed in Moisture Tracking Tool
Moisture Tracking Tool
Progress % = (Start - Current) / (Start - Target) x 100Used in Moisture Tracking Tool
Kiln Schedule Finder
Kiln Schedule Finder
Drying time ~ k x Thickness^2 x severity_factor x ln(MC1/MC2)Used in Kiln Schedule Finder
Kiln Schedule Finder
Schedule steps decrease wet-bulb (raise temp) as MC dropsUsed in Kiln Schedule Finder
Kiln Schedule Finder
Target EMC at each step is set ~2-4% below current wood MCUsed in Kiln Schedule Finder
Shrinkage Predictor
Shrinkage Predictor
where S_total = radial or tangential total shrinkage coefficientUsed in Shrinkage Predictor
Shrinkage Predictor
Volumetric ~ Radial% + Tangential% (small-strain approximation)Used in Shrinkage Predictor
Shrinkage Predictor
T/R ratio = Tangential / Radial (warp risk: under 1.5 stable, over 2.0 high)Used in Shrinkage Predictor
EMC Calculator
EMC Calculator
EMC = (1800/W) x [kh/(1-kh) + (k1kh + 2k1k2k^2h^2)/(1 + k1kh + k1k2k^2h^2)]Used in EMC Calculator
Acclimation Calculator
Acclimation Calculator
Target EMC from room T and RH (Hailwood-Horrobin)Used in Acclimation Calculator
Acclimation Calculator
Acclimation days ~ base x thickness_factor x gap_factor x airflow_factorUsed in Acclimation Calculator
Acclimation Calculator
Thicker boards and poor airflow increase the time sharplyUsed in Acclimation Calculator
Fiber Saturation Calculator
Fiber Saturation Calculator
MC from mass = (Wet mass - Oven-dry mass) / Oven-dry mass x 100Used in Fiber Saturation Calculator
Fiber Saturation Calculator
FSP temperature adjust = FSP_20 - 0.1 x (T - 20) (T in deg C)Used in Fiber Saturation Calculator
Fiber Saturation Calculator
Free water (above FSP) = max(0, MC - FSP)Used in Fiber Saturation Calculator
Common questions
Where do these formulas come from?
Every formula on this page comes from a published source — standards, handbooks or long-established trade rules for moisture and wood science. The source is named next to each formula. Nothing here is invented by us.
Can I use these formulas in my own spreadsheets or software?
Yes. The formulas themselves are public knowledge and free to use anywhere. If our page helped you, a link back is appreciated but not required.
Are the calculators on this site using these exact formulas?
Yes. Each calculator runs the formula shown here, and automated tests check the results against worked examples from the original sources before anything goes live.