Concrete Load Calculator
This concrete load calculator estimates what a slab-on-grade can carry: allowable interior point load and uniform load, computed with the Westergaard interior-load equations and PCA method from thickness, concrete strength and subgrade support — with every assumption stated.
Comment utiliser ce calculateur
- Saisissez vos dimensions — pieds pour les longueurs, pouces pour l'épaisseur.
- Ajustez les options — pourcentage de perte, taille du sac et prix local du béton.
- Lisez vos résultats — le volume, les sacs, le poids et le coût se mettent à jour en direct.
La formule
MOR = 7.5√f'c ÷ SF 2.0; ℓ = [Et³/12(1−ν²)k]^0.25; P = σ_allow·2πt² ÷ [3(1+ν)(ln(ℓ/b)+0.6159)] Exemple résolu : A 4 in slab, 3,000 psi concrete on fair subgrade (k=100), 6 in load radius: allowable interior point load ≈ 5,000–6,000 lb — a loaded pickup wheel is fine; a loaded skid-steer may not be.
A slab capacity calculator has to respect where the load sits: these results are for interior loading, away from edges and joints. Edge and corner loads stress a slab roughly 1.5–2× more — keep heavy wheels off unsupported edges.
Thickness dominates: capacity scales roughly with t², so a 6-inch slab carries about 2.25× the point load of a 4-inch slab in the same conditions. Subgrade is next — a slab is only as strong as what's under it.
This concrete slab load calculator is an informational screening tool using unreinforced flexural capacity with a 2.0 safety factor. Reinforcement adds crack control and post-crack capacity but the uncracked estimate governs serviceability.
Foire aux questions
Questions courantes sur le concrete load calculator.
How much weight can a 4 inch slab hold?
On decent subgrade with 3,000 psi concrete: interior point loads in the ~5,000 lb range per wheel/leg (with safety factor). Passenger vehicles are fine; concentrated racking or equipment legs need checking.
How much more can a 6 inch slab carry?
Point capacity scales with thickness squared: a 6 in slab carries roughly 2.25× a 4 in slab — typically 11,000+ lb interior point loads on good subgrade.
Why does subgrade matter so much?
The slab spreads load into the ground; soft subgrade lets the slab bend further, raising flexural stress. Doubling k (subgrade modulus) meaningfully raises capacity — compaction is cheap strength.
Can I use this for a suspended slab?
No — this tool models slab-on-grade only. Suspended/elevated slabs are structural members requiring engineered design.
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