Framing
Stud / joist centre spacing
- where
- bays
- end-centre span (mm)
- maximum specified centres (mm)
- members
- actual centres (mm)
Explain this equation
Spaces studs or joists equally between two end members without exceeding a maximum centre spacing.
S is the span between the centre lines of the two end members, in millimetres. cmax is the largest centre spacing allowed. b is the number of bays, N the number of members and c the actual equal centres.
Dividing the span by the maximum and rounding up with ⌈ ⌉ gives the fewest bays that keep every spacing within the limit. There is always one more member than bays, because both ends need one. Sharing the span equally across the bays gives the actual centres.
A 3600 mm span at 400 mm maximum is exactly 9 bays: 10 members at 400 mm. At 3700 mm you would need 10 bays at 370 mm, with 11 members.
Watch out: the span runs centre to centre, not across the outside of the frame. Extra studs at corners and openings are separate.
Distribute equal bays between two end-member centre lines.
Enter your values to see the result.
Good to know
Span is between end centres, not the outside frame size. Extra corner studs, trimmers, lintels and openings are separate. This does not choose a structural spacing.
Sources
- Geometry / arithmetic
This is a calculation aid, not a structural design or compliance certificate. Every default is an example, not a specification for your project.