Moisture content risk
Wood that is too wet will shrink after you build with it. Wood that is too dry for its environment will swell. Either way, you've made a project that won't stay flat. This calculator compares your stock's current moisture content against the equilibrium moisture content of the room it will live in, and gives you a risk tier plus concrete recommendations.
Calculator
Why MC matters more than most beginners think
A 1% change in moisture content moves a flat-sawn oak board by roughly 1% of its width. For a 24″ tabletop, that's ~0.24″ — a quarter inch. Across a glued-up panel, that movement doesn't happen in the joint, it happens between the joints. The boards shrink apart, gaps open, and your carefully fitted piece looks like a workbench.
Moisture content is also why "kiln dried" and "ready to use" are not the same thing. Kiln-dried at 7% MC is right for a climate-controlled interior. The same board in a damp basement shop is going to pick up moisture and grow back.
A practical rule of thumb
For furniture in a climate-controlled interior, target 6–8% MC. For cabinetry in a normal home, target 8–10%. For outdoor projects, "whatever the lumber is at" is fine — design for movement instead.
To acclimate stock, sticker it in the room it will live in for at least 1 week per inch of thickness. 8/4 walnut wants 8 weeks; 4/4 poplar wants 4 weeks. Measure MC with a real meter — pinless is faster and non-marking.
Limitations
- EMC tables assume constant RH and T. Real basements cycle seasonally; the right "target" shifts through the year.
- Meter accuracy varies by ±0.5–1% across devices and species. Calibrate against a known sample if precision matters.
- Stock dried at the surface can be 2% wetter in the core. The meter reads the surface; trust the higher of two readings on thick stock.
- Surfacing changes things: a planed board equilibrates faster than a rough one.
Frequently asked questions
How long does it really take to acclimate 4/4 stock?
Rule of thumb: 1 week per inch of thickness, with stickers every 12–16″ and good airflow on all sides. 4/4 stock with proper stickering typically reaches equilibrium in 4–6 weeks; kiln-dried stock that came in already near the room's EMC may only need 1–2 weeks.
Can I just kiln-dry it myself with a dehumidifier?
For drying green wood, no — you'll case-harden the outside and trap moisture inside. For bringing kiln-dried stock down a few percent to match your shop, a dehumidifier in a closed room will work over a few weeks. Commercially kiln-dried lumber usually arrives within 1–2% of the moisture content your meter reads in a normal shop.
My meter says 12% but the wood feels dry. What's going on?
Either your meter is calibrated for a different species (most are calibrated for Douglas fir; softwoods read artificially high), or you're feeling the surface while the core is wet. Try the same board at 1/2 the thickness and see if the number changes.