`"iJC" = (( W *12) / ( 16 ) + 1) +"adder"`

Enter a value for all fields

The I-joist Calculator computes the number of i-joists are required for a floor based on the dimension of the room. The user can also enter the on-center separation of joists, but the system has 16" on-center separation as the default.

INSTRUCTIONS: Choose your preferred units and enter the following:

• (W) Floor Width (crossing the joists)
• (oC) On-Center spacing (separation of joists)

I-Joists Count (iJC): The calculator returns the number of I-joists needed for the floor.

NOTES

This algorithm makes no assumptions for the maximum span.  It is assumed that joist of the appropriate span can be found (steel, I-joists, or other materials).  This equations only provides the number of the spanning joists (brown-red in diagram) and not those on the very edges (e.g. first and last plates).  See diagram.  It does assume that the first and last i-joist are right next to the edge plates.

---

Building Calculators

• Total Building Materials Calculator
• Total Pole Barn Materials Calculator

• Area of a Roof
• Pitch of a Roof
• Number of Trusses Needed for a Roof
• 4x8s needed for a roof
• Shingles needed for a roof
• Number and Length of Metal Roof Panels
• Number and Length of Purlins
• Number and Length of Rafters
• Number and Length of Rafter and Collar ties

• Number and Length of wall top and bottom wall plates
• Number of Studs for a Room
• Number of Studs in a Wall
• Room Interior Area (wall and ceiling)
• Cubic Feet in a Room (volume)
• Number of 4x8 or 4x12 Sheets for a Room

• Number and Length of Floor Joists
• Number of Joist Hangers
• Compute the Cost of Floor Joists
• Compute iJoists for larger floors
• Compute the Number of 4x8 Sheets to cover the Deck or Floor
• Compute the number of Decking Boards to cover the deck or floor