Timber Connection Calculators
Free tools for checking timber and wood-screw connections — withdrawal and shear capacity, and fastener spacing with edge and end distances. Based on Eurocode 5, NDS 2018 and IS 883:2016.
A timber connection has two things to check: whether each fastener can carry its load, and whether the fasteners are spaced far enough apart that the wood does not split. Pick the calculator that matches your question below. These are engineering aids for checking a connection, not a substitute for a full structural design by a qualified engineer.
Screw Withdrawal & Shear Strength Calculator
Timber Screw Spacing Calculator
Which calculator do you need?
Use the Screw Withdrawal & Shear Strength calculator when you know the fasteners and want to check how much load each one can carry, in withdrawal (pull-out) or shear (lateral), for a given species and diameter.
Use the Timber Screw Spacing calculator when you want to check the minimum spacing between fasteners, and their edge and end distances, so the timber does not split or tear out. A full connection check usually needs both.
A free alternative for timber connection checks
Commercial timber-connection software is powerful but often paid and tied to a single design code. These Vriksai calculators are free and cover the common Eurocode 5, NDS and IS 883 checks for wood-screw and fastener connections, which is enough for many everyday checks and for learning how the numbers behave. For a complete connection design — combining capacity, spacing, load duration, service condition and failure-mode checks under a limit-states approach — use the full design standard and have the result reviewed by a qualified structural engineer.
What these calculators do not cover
These tools handle wood screws, lag screws, nails and bolts in the checks described above. They do not yet cover specialised connectors such as timber rivets, split rings, shear plates or proprietary connection systems, and they do not perform full limit-states connection design or brittle failure-mode checks (row shear, group tear-out). Always confirm a structural connection against the applicable building code and standard for your region.