Foundations
& Footings
Calculators
Every below-grade concrete element in one place — from a simple post hole to a full foundation wall system. 10 free tools sized for homeowners, builders, and structural engineers.
All 10 Foundation & Footing Calculators
Accurate concrete volume for every below-grade pour — footings, walls, piers, post holes, piles, and more. Free, no login required.
Calculate concrete volume for strip footings, pad footings, and spread footings. Enter width, depth, and length (or number of pads) to get cubic yards and bag count. Supports continuous perimeter footings and isolated column footings in a single session — the starting point for any foundation estimate.
Calculate concrete bags for round or square post holes. Enter hole diameter or width, depth, and post size — the tool subtracts the post volume and outputs bags per hole and a total order quantity for any number of posts.
Calculate concrete volume for cylindrical tube forms (Sonotube, Quik-Tube, and similar). Enter tube diameter and pour height, select the number of tubes, and get cubic yards and 60-lb or 80-lb bag count with one click.
Calculate volume for poured concrete foundation walls. Enter wall length, height, and thickness for each wall segment. Supports L-shaped and U-shaped perimeters, and deducts openings for windows and access points.
Calculate concrete for square, rectangular, or round columns and piers. Enter cross-section dimensions and column height. Handles multiple columns simultaneously and outputs both volume and bag count per column and in total.
Calculate concrete for a basement floor slab including irregular shapes and step-down areas. Enter room dimensions and slab thickness, subtract any mechanical trenches, and get total cubic yards with a waste factor recommendation.
Calculate concrete volume for gravity and cantilever retaining walls. Enter wall height, base width, stem thickness, and total length. Includes footing volume in the same calculation and supports tapered wall profiles. Ideal for landscape retaining, grade changes, and site-work applications up to 10 feet in height.
Calculate concrete for a stem wall foundation — a footing-and-wall combination used in raised-floor and crawl-space construction. Enter perimeter, wall height, wall thickness, and footing dimensions to get a combined volume in one pass.
Look up the required footing depth for your location based on USDA frost depth maps and IRC/IBC minimums. Enter your zip code or state, soil type, and load condition to get the minimum code-compliant footing depth — critical for any foundation in a freeze-thaw climate.
Calculate concrete volume for cast-in-place drilled piles and bored piers. Enter pile diameter, depth, bell diameter (if belled), and pile count. Outputs total volume and accounts for cage displacement — used for deep foundation and high-load applications.
How to Calculate Concrete for Foundations & Footings
Foundation concrete calculations differ from flatwork because the geometry is more varied — strip footings, isolated pad footings, round piers, and poured walls all use different volume formulas — and the stakes for under-ordering are higher. A cold joint in a footing or foundation wall is a structural defect, not just an aesthetic one.
For strip and continuous footings, the formula is straightforward: width × depth × total length. Always add a 5–10% waste factor for form irregularities and subgrade variation. For isolated pad footings under columns, calculate each pad separately (length × width × depth) and sum them — our Footing Calculator handles both in one session.
Round elements — Sonotubes, drilled piers, and round columns — use the cylinder formula: π × r² × height. This is where manual calculation errors are most common; a 12-inch vs 14-inch tube is easy to confuse but results in a 36% volume difference. Use the Sonotube Calculator to avoid that mistake.
One step most DIYers skip: always verify footing depth against the frost line for your location before ordering. Footings poured above the frost depth will heave in winter and fail. Use the Frost Depth Calculator to look up the code-required minimum depth for your zip code before you dig.
Foundations & Footings FAQ
Answers to the most common concrete foundation and footing calculation questions.
Footing depth depends on frost depth, soil bearing capacity, and the load it carries. In cold climates, footings must extend below the frost line — typically 36–48 inches in northern US states — to prevent heave. In frost-free regions, a minimum 12-inch depth below undisturbed soil is standard. Use the Frost Depth & Footing Depth Calculator to look up the requirement for your location.
The volume of concrete per post hole depends on hole diameter, depth, and post size. A common 10-inch diameter hole at 36 inches deep with a 4×4 post requires roughly 0.06 cubic yards — about 1.5 80-lb bags. Multiply by your post count for the total order. The Post Hole Calculator handles round and square holes, multiple posts, and outputs both bag count and cubic yards.
A footing is the wider, flat base that spreads the structure's load across the soil — always below frost depth and typically wider than the wall above it. A foundation wall sits on top of the footing and transfers loads from the structure down to it. Both need separate concrete volume calculations because they have different shapes. Use the Footing Calculator for the base and the Foundation Wall Calculator for the vertical wall.
Round column volume uses the cylinder formula: π × (diameter ÷ 2)² × height. For a 12-inch Sonotube at 4 feet tall that equals approximately 3.14 cubic feet, or 0.116 cubic yards. Our Sonotube & Column Calculator handles this automatically for any diameter and height and lets you calculate multiple tubes at once.