What is dead load vs. live load?

Dead load (D) is the permanent weight of structural components — slabs, beams, columns, cladding. Live load (L) is transient occupancy load — people, furniture, equipment. Both act on the foundation simultaneously.

Why multiply by tributary area?

Load intensities are given in force per unit area (kPa or psf). Multiplying by the tributary area converts them to the total point load carried by one foundation element.

What is the ACI 318 factored load combination used here?

The calculator uses U = 1.2D + 1.6L + 0.5S, which is the governing ACI 318-19 combination for gravity loads when snow (S) is present. For no snow, it reduces to 1.2D + 1.6L.

Should I include the foundation self-weight in bearing capacity checks?

Yes. The footing and soil above it add to the gross load. This calculator totals that load, but an actual soil bearing pressure also requires the footing contact area, which is not the tributary floor area entered here.

What units does the calculator support?

You can work in either SI (kN/m² and m²) or US customary (psf and ft²). Select your unit system and the calculator handles conversions automatically.

Foundation Load Calculator

Enter dead load, live load, snow load, and foundation self-weight to get the total factored and unfactored vertical loads for foundation design.

Load Inputs

Unit System

Tributary Area (m²)

Floor area supported by this foundation element.

Dead Load Intensity (kN/m²)

Typical range: 3–8 kN/m² (60–165 psf) for concrete floors.

Live Load Intensity (kN/m²)

Residential: 1.9–2.4 kN/m²; Office: 2.4–4.8 kN/m².

Snow Load Intensity (kN/m²) (optional)

Foundation Self-Weight (kN) (optional)

Weight of the footing itself (concrete volume × 24 kN/m³).

Enter load values and click Calculate to see results.

Load Breakdown

Load Component	Intensity	Total

Unfactored Total Load

—

D + L + S + Self-weight

Equivalent tributary load intensity

—

Factored Load (ACI 318)

—

1.2D + 1.6L + 0.5S

Governs concrete design

Use for rebar / footing sizing

Calculation Summary

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Summary

Enter dead load, live load, snow load, and foundation self-weight to get the total factored and unfactored vertical loads for foundation design.

How it works

Enter the tributary area the foundation supports (in square feet or meters).
Input dead load intensity (structural weight, permanent fixtures).
Input live load intensity (occupancy, furniture, movable loads).
Optionally enter snow load and the foundation self-weight.
The calculator outputs total unfactored load and ACI 318 factored load (1.2D + 1.6L + 0.5S).
Use the factored load for concrete/steel design; divide the unfactored load by the actual footing area for a soil bearing-pressure check.

Use cases

Size a spread footing for a residential column.
Supply the service load needed for a separate footing bearing-capacity check.
Determine factored design load per ACI 318 load combinations.
Compare load scenarios when varying slab thickness or occupancy class.
Quick sanity-check of hand calculations during preliminary design.
Teaching structural load path concepts in civil engineering courses.

Frequently Asked Questions

Last updated: 2026-09-20 · Reviewed by Nham Vu