#4 vs #5 Rebar: Which Should You Use?
Compare #4 vs #5 rebar for slabs-on-grade, including diameter, typical applications, and when heavier bar is justified.
Quick comparison
#4 is common for many slabs-on-grade. #5 is typically used when higher loads, longer spans, or engineered requirements exist.
When #5 is justified
Industrial slabs, point loads, thicker sections, or designs calling for more steel area may justify #5.
Avoid overbuilding without engineering
More steel doesn’t fix base or joint issues. Follow a coherent plan (thickness + base + joints + curing).
Fast path: Use the slab thickness calculator for a coherent recommendation, then confirm rebar spacing and volume.