Calculate the number of floor or ceiling joists needed for your framing project. Enter the span length, joist spacing, and the direction of the joists to determine quantities. This calculator helps you plan lumber orders for floors, ceilings, and deck framing.
Enter Your Measurements
Results
Total Joists (incl. rim)
18
joists
Field Joists
16
joists
Rim Joists
2
joists
Total Linear Feet
232
ft
Framing Area
240
sq ft
Formula
How to Use This Calculator
How to Use
- 1
Enter the span length (the direction joists run, from bearing wall to bearing wall).
- 2
Enter the frame width (perpendicular to the joists).
- 3
Select the joist spacing (16 inches OC is standard for floors, 24 for some ceilings).
- 4
Include rim joists if framing a complete floor system.
Frequently Asked Questions
Frequently Asked Questions
What size joists do I need?
Can I use 24-inch joist spacing for floors?
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About This Calculator
This calculator uses the formula: Joists = (Frame Width × 12 ÷ Spacing) + 1 + Rim Joists. All calculations follow industry-standard methods. Results are estimates — always verify with a licensed professional for structural or code-compliant work.
Built and maintained by the CalcSmart team. Last updated March 2026.
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