Skip to main content
Calcimator

Steel Joist Selection Calculator

Select a steel joist designation per SJI K-Series tables based on span, tributary width, and loading conditions.

Inputs

ft
ft
psf
psf

Results

Total Uniform Load

600 plf

Live Uniform Load300 plf
Joist Weight (est.)8.6 plf
Allowable Deflection (L/360)1 in
Required Moment of Inertia188.5 in⁴
Deflection Ratio360%
How to Use This Calculator
  1. Enter the clear joist span in ft and the tributary width (center-to-center joist spacing) in ft.
  2. Set the total design load in psf (dead + live + superimposed) and the unfactored live load in psf for deflection.
  3. Read Total Uniform Load (plf) — this is the value you match against SJI load tables to pick a joist designation.
  4. Check Allowable Deflection (L/360) in inches and Required Moment of Inertia to confirm serviceability.
  5. Use Joist Weight (est.) per linear foot to include self-weight in your structural dead load.
  6. Cross-reference the calculated values with your SJI K-Series or LH-Series load tables to finalize the designation.

How the result changes with Tributary Width

Tributary WidthTotal Uniform Load
3.9390 plf
111,100 plf
202,000 plf
272,700 plf

What each input means

Joist Span
Clear span of the joist in feet.
Tributary Width
Joist spacing (tributary width) in feet.
Total Load
Total design load including dead, live, and superimposed loads (psf).
Live Load
Unfactored live load for deflection check (psf).

What each result means

Total Uniform Load
Total load per linear foot on the joist.
Live Uniform Load
Live load per linear foot for deflection calculations.
Joist Weight (est.)
Estimated joist weight per linear foot from SJI tables.
Allowable Deflection (L/360)
Maximum allowable live load deflection.
Required Moment of Inertia
Minimum required moment of inertia for deflection control.

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Joist Span = 30, Tributary Width = 6, Total Load = 100, Live Load = 50 = 4 input(s) provided
  2. Calculate Total Uniform Load
    Total Uniform Load = totalLoad * tributaryWidth
    600 = 600
  3. Calculate Live Uniform Load
    Live Uniform Load = liveLoad * tributaryWidth
    300 = 300
  4. Calculate Joist Weight
    8.6 = 8.6

Engine last updated . Checked against 3 independently-derived tests — how we verify calculators.

Related Calculators

The questions that sit next to this one — chosen by subject, including calculators filed under a different category.

Steel Construction

Structural Steel Cost Calculator

Estimate total installed structural steel cost including material, fabrication, erection, connections, and miscellaneous metals.

Steel Construction

Metal Deck Calculator

Calculate metal deck sheet count, shear studs, pour stop, and material weight for composite or roof deck installations.

Steel Construction

Steel Takeoff Calculator

Calculate total steel tonnage from beam and column counts, weights, and lengths for quantity takeoff estimates.

More in Construction & Building Trades.