Estimate deck joist span, joist spacing, deck line load, total joist load, support reactions, maximum bending moment, shear stress, bending stress, deflection, and simplified maximum span. Use this deck joist calculator for deck framing, porch floors, platform framing, outdoor structures, and preliminary structural planning.
Load conversion:
The calculator converts deck dead load, live load, and snow or extra load in PSF into a line load using joist spacing.
Joist section:
The calculator uses actual joist width and depth to estimate area, section modulus, and moment of inertia.
Strength checks:
The calculator estimates bending stress and shear stress, then compares them to entered allowable values.
Deflection check:
The calculator estimates joist deflection and compares it to the selected span limit.
A deck joist calculator helps estimate whether a deck joist size, spacing, and span may be reasonable for a given deck load.
It can help compare deck load, joist spacing, line load, total load, support reactions, bending, shear, deflection, and estimated maximum span.
Your result shows estimated joist line load, total load per joist, support reactions, maximum shear, maximum moment, bending stress, shear stress, deflection, allowable deflection, span ratio, and estimated maximum joist span. These are planning estimates only.
A deck joist is a horizontal framing member that supports deck boards and transfers deck loads to beams, ledgers, hangers, or supports.
Multiply the deck load in PSF by joist spacing in feet, then add joist or decking self weight. For example, 50 PSF at 16 inches on center is about 66.7 PLF before self weight.
Deck joist span can be controlled by bending, shear, deflection, joist size, species, grade, spacing, load, moisture exposure, and local code requirements.
No. Final deck joist sizing should use approved span tables, local building code, lumber species and grade, fastener requirements, joist hangers, ledger details, beam layout, and professional review when needed.