Grainsway: Wood Movement Calc

Grainsway works out how much solid wood will move, offline.

Enter a board's width, species and sawing orientation, then the moisture change it will see - either a start and end moisture content, or room humidity and temperature at each end - and see exactly how much it will swell or shrink, in millimetres or inches. Then turn that into the gap, groove or slot a panel, breadboard end or tabletop fastener needs, so it never splits or shows a gap.

CALCULATE
• Board width (mm or in, inch fractions accepted), from 68 built-in species or your own custom species
• Sawing orientation: flat-sawn, quarter-sawn or rift-sawn, each with its own movement coefficient
• Moisture: type a start and end moisture content, or room relative humidity and temperature (°C or °F) - converted to equilibrium moisture content with the Hailwood-Horrobin equation the Wood Handbook uses
• Movement and end width, or a full winter-to-summer seasonal range
• A warning when a result is clamped at the species' fibre saturation point, or extrapolated beyond the humidity table

ALLOWANCES
• Floating panel: the groove depth and the gap per side, so the panel never bursts the frame in summer or shows a gap in winter
• Breadboard end: the elongated peg slot each outer peg needs for the top's movement away from the centre
• Tabletop fasteners: the clearance a slotted or figure-8 fastener needs, with a warning if a figure-8 would swing too far

PROJECTS
• Save any board to a project, with notes
• Several boards per project; rename, duplicate or delete, with undo
• Back up every project to a file you choose, and restore it later, through the share sheet

SETTINGS
• Metric or imperial units, a default sawing orientation, light or dark theme
• A short glossary of flat/quarter/rift-sawn, relative humidity, EMC and fibre saturation point

NO ADS. NO SUBSCRIPTION. NO ACCOUNT.
Pay once. There is no advertising, no in-app purchase and no sign-in. Grainsway never asks for bank or card details.

WORKS OFFLINE, STAYS ON YOUR PHONE
Grainsway has no internet permission, so it cannot send your projects anywhere. Everything stays on your phone.

BUILT ON PUBLISHED DATA
Movement coefficients and the EMC method are from the USDA Forest Products Laboratory Wood Handbook, a public-domain reference. Grainsway is a planning aid, not a substitute for a moisture meter or your own test boards on an unfamiliar species.

Recent changes:
Performance improvements: smaller app size and faster start.