Shear Force Calculator Formula
Understand the math behind the shear force calculator. Each variable explained with a worked example.
Formulas Used
Each Reaction
reaction = total_load / 2Max Shear Force
max_shear = total_load / 2Total Load
total_load_out = total_loadVariables
| Variable | Description | Default |
|---|---|---|
span | Beam Span(ft) | 16 |
load_plf | Uniform Load(lb/ft) | 300 |
total_load | Derived value= span * load_plf | calculated |
How It Works
Shear Force (Simply Supported Beam)
V_max = wL / 2
For a simply supported beam with uniform load, the maximum shear force occurs at the supports and equals half the total load. The shear force decreases linearly to zero at mid-span.
Worked Example
16 ft beam with 300 lb/ft uniform load.
span = 16load_plf = 300
- 01Total load = 16 x 300 = 4,800 lbs
- 02Reaction at each support = 4800 / 2 = 2,400 lbs
- 03Max shear = 2,400 lbs (at each support)
Frequently Asked Questions
Where is shear force highest?
For a uniformly loaded simply supported beam, maximum shear occurs at the supports. For point loads, shear is highest between the load point and the nearest support.
Why does shear matter?
Shear failures cause the beam to split horizontally near the supports. Wood beams are particularly susceptible because wood is weak in horizontal shear along the grain.
Ready to run the numbers?
Open Shear Force Calculator