A few years ago I created an online calculator for predicting how much lumber will expand or contract based on its percent moisture content (MC). I personally use it quite a bit! The calculator requires a starting %MC and a final %MC in order to calculate how much wood movement will occur. Unfortunately, sometimes it can tricky to predict a final %MC based on where in the country the piece of furniture will live.

In order to help with deciding on a final %MC there are equations that one can use (the equations have been previously published link). In order to simplify the calculations, I created an online calculator which allows you to enter your ambient air temperature and the relative humidity; the calculator will provide the %EMC (equilibrium moisture content) from these values. You could, in theory, use a relative humidity and temperature that would represent the largest deviation based on where your piece of furniture will live.

So if you know your starting %MC via the use of a moisture meter, you could then use the EMC calculator to come up with a final %MC in order to calculate how much expansion or contraction the wood might incur.

If you have any questions please let me know below.

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on Friday, June 7th, 2019 at 10:31 am and is filed under Lumber.
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Wow! Great Tool! I have been trying to do everything with some mental math but with a big project coming up I wanted to be more precise. Thank you!