Skip to main content

Reinforced concrete beam and 1-way slab calculator

Jonathan Ochshorn

contact | academic homepage | Structural Elements text | calculator homepage

Directions: Enter values for design (factored) moment, beam "stem" width, bw, effective depth, d, span, spacing, and slab thickness (not all parameters are used for all calculations). Note that design moment for slabs is calculated on a typical 1-ft wide section of the slab. Press "update" button.

The required reinforcement area, As, will be calculated (for slabs, the required spacing of a selected bar size is calculated). More detailed explanations and examples of reinforced concrete beam and slab design can be found in my text.

Note that the strength design method is used; moments must be computed based on factored loads.

Calculator works for rectangular beams, positive-moment and negative-moment T-beams, and 1-way slabs, as shown in the sections below:

reinforced concrete beam sections
Fig. 1. Reinforced concrete beam sections: a) positive-moment rectangular beam; b) negative-moment rectangular beam; c) negative-moment T-beam; and d) positive-moment T-beam

Mu units d (in.) f'c (ksi) fy (ksi)
beam type As (sq in.)
  Effective width:
rho must be <= rho max  
slab spacing must be 2" min.  
d must be >= slab thickness for beams  
beam span must be > 0  
stem width must be > 0  
effective depth, d, must be > 0  
centerline spacing must be > stem width