Free Contractor Tool · Sign Foundation Calculator

Sign Foundation Calculator

Estimate wind load, footing size, concrete, and spoil for freestanding signs.

Use this sign foundation calculator — also useful as a pole sign foundation calculator or pylon sign foundation calculator — to estimate a starting foundation size for freestanding signs under approximately 35 ft tall. Add each sign section that catches wind — cabinets, reader boards, toppers, or solid panels — and the tool will estimate your hole size, concrete volume, and spoil.

This tool is for preliminary planning and quoting. Local codes, landlords, and permitting authorities may still require engineered drawings.

Step 0

How Is the Pole Being Installed?

Step 1

Wind & Site Conditions

Basic Wind Speed (V)

ASCE 7-22 §26.5 ultimate wind speed.

Exposure Category

Step 2

Sign Dimensions

Sign Face Width — B (ft)

Sign Face Height — s (ft)

Total Structure Height (ft)

The full height from grade to the very top of the sign. The calculator determines where the sign face sits based on this and the sign height.

Step 3

Support Configuration

Number of Support Poles

Pole Diameter (in)

The outer diameter of the pole above grade in inches. Used to compute wind load on the exposed column.

Step 4

Foundation Parameters

Method A — Pole Set in Concrete

The same pole runs from below grade up to the sign. Drill the hole, drop the pole in, pour concrete around it.

Soil Type (IBC Table 1806.2)

Use the diameter results table below to compare all options side by side.

Maximum Drill Depth — ft (optional)

Set a maximum depth in feet if your equipment or site conditions limit how deep you can drill.

Add Belled BaseA belled base increases moment capacity and can reduce required shaft depth by 20–30%. Bell geometry: outer radius = pier diameter, height = 0.5× pier diameter. Ask your driller if belling is practical for your soil.

Related Tool

Concrete Hole Volume Calculator

Need to calculate concrete for drilled holes only? Use our concrete hole volume calculator for holes, slabs, and spoil estimates.

Open Concrete Calculator →

This calculator implements ASCE 7-22 wind pressure calculations and IBC 1807.3 embedment depth equations for preliminary planning purposes. For signs with effective load heights above 12 ft, a full p-y curve analysis and licensed structural engineer stamp are required for permitting in all U.S. jurisdictions. Final design requires a geotechnical report with site-specific soil parameters. Minimum concrete specification: 4,000 psi. Always verify with your local building department before breaking ground.

How It Works

How the Sign Foundation Calculator Works

This sign hole size calculator uses basic wind engineering principles to estimate the overturning moment your sign will exert on its foundation. The overturning moment — measured in foot-pounds — is the rotational force the wind applies at the base of the sign pole or column. A larger or taller sign creates a larger moment and requires a deeper, wider footing.

The wind pressure (q) is calculated as q = 0.00256 × V², where V is wind speed in miles per hour. For each section of sign, the tool calculates force (q × face multiplier × area) and moment (force × center height above grade). All section moments sum to the total overturning moment, which the tool maps to a starting foundation size.

This is a sign wind load calculator for preliminary quoting — not a substitute for engineered drawings. For signs above approximately 35 ft, unusual geometries, or moments above 60,000 ft-lbs, a licensed engineer should specify the foundation. Use this tool to plan your drilling quote and materials, then let the engineer finalize the spec.