Grade Beam Calculator

1. Enter the beam length in feet, and the width and depth in inches.
2. Enter the number of beams and the number of longitudinal bars.
3. Set the cover and a waste allowance.
4. Read the concrete volume in cubic yards, the bag count, and the rebar estimate.

Here is what each result line means:

A grade beam calculator estimates the concrete and reinforcing steel for a grade beam. A grade beam is a reinforced concrete beam at or near ground level that spans between piers, piles or footings and carries a wall or column load across weak soil.

It multiplies the beam cross section by its length and the number of beams for the concrete, and totals the main longitudinal bars for the steel. To estimate the piers the beam spans between, use the Sonotube calculator for round pier forms.

The concrete is the cross section times the length times the number of beams. The rebar is the main bars running the length, less the end cover.

1. Convert the width and depth to feet and multiply by the length for one beam volume.
2. Multiply by the number of beams and add the waste allowance.
3. Divide by 27 to convert cubic feet to cubic yards.
4. For rebar, multiply the number of longitudinal bars by the beam length less end cover, times the beam count.

The rebar figure covers the straight longitudinal bars only. Stirrups, laps and development lengths come from the structural drawings.

Suppose you are pouring one grade beam 20 feet long, 12 inches wide and 24 inches deep, with 4 longitudinal bars, 3 inch cover, and a 10 percent waste allowance.

Calculation: the cross section is 1 foot by 2 feet, so the beam is 20 times 1 times 2, which is 40 cubic feet. Adding 10 percent and dividing by 27 gives about 1.63 cubic yards. The rebar is 4 bars times about 19.5 feet, roughly 78 feet of bar.

The lesson: the cross section and length set the concrete, while the bar count sets the steel, so enter the values from your drawings.

Cross Section

Width and depth multiply together, so a deeper or wider beam uses noticeably more concrete per foot of length.

Length and Beam Count

The total scales directly with how long the beams are and how many you pour. Count every run, including returns and short beams.

Longitudinal Bars

More main bars mean more steel. The number, top and bottom, comes from the structural design, not a rule of thumb.

Over-excavation and Waste

Grade beams are often cast against earth in a trench, so some extra concrete is normal where the trench is wider or deeper than planned.

A grade beam and a strip footing both run in a line, but they work differently, which affects how they are built.

A grade beam carries load across soft ground to the piers, so it is more heavily reinforced than a strip footing that simply rests on good soil.

Ordering Concrete

Turn beam sizes into cubic yards to order ready-mix, or bags for a small run.

Estimating Rebar

Get a planning figure for the main longitudinal steel.

Checking a Plan

Sanity-check a materials list against the drawings before pour day.

1. Guessing the Size

Grade beam dimensions and reinforcement are designed for the span and load. Use the drawings, not a guess.

2. Counting Only the Longitudinal Bars

Stirrups add steel this tool does not estimate. Read the full rebar schedule for ordering.

3. Forgetting Over-excavation

Trenches are rarely exact. A waste allowance covers the extra concrete where the trench is oversized.

4. Using Too Little Cover

Concrete cast against earth needs about 3 inches of cover to protect the steel from the soil.

5. Confusing It with a Strip Footing

A grade beam spans between supports; a strip footing bears on soil. They are reinforced differently.

The volume math is exact for the dimensions you enter. The rebar figure is a simple longitudinal estimate, and beam design is an engineering task.

Multiply the length by the width and depth in feet, then by the number of beams, and add waste. A 20-foot beam, 12 by 24 inches, needs about 1.6 cubic yards, or around 74 eighty-pound bags, with 10 percent waste.

A grade beam is a reinforced concrete beam at ground level that spans between piers, piles or footings. It carries a wall or column load across soft or expansive soil to the deeper supports.

A footing bears directly on the soil beneath it, while a grade beam spans between supports like a beam. Because it bridges weak ground, a grade beam is more heavily reinforced than a strip footing.

Grade beams have main longitudinal bars top and bottom, plus stirrups. This tool estimates the longitudinal bar length from the number you enter, but the full schedule, including stirrups and laps, comes from the structural drawings.

Sizes vary with the span and load, often from about 10 to 16 inches wide and 18 to 36 inches deep in residential work. Your engineer sets the exact size, so enter the specified dimensions.

For concrete cast against and permanently exposed to earth, ACI uses 3 inches of clear cover. Grade beams are often poured in trenches against soil, so the tool defaults the cover to 3 inches.

For a short beam, yes, and the tool shows a bag count. Longer beams need a lot of concrete at once, so ready-mix is usually better for a continuous, monolithic pour.

The concrete volume is exact for your dimensions. The rebar figure is a longitudinal-only planning estimate, so treat it as a guide and order from the full rebar schedule.

No. The calculation runs entirely in your browser and nothing you enter is stored or sent anywhere.

• QUIKRETE Concrete Mix (No. 1101) data sheet (bag yields: 80 lb ~0.60 cu ft, 60 lb ~0.45, 40 lb ~0.30).
• American Concrete Institute (ACI 318; concrete cover for members cast against earth).
• American Cement Association (American Cement Association; grade beams and deep foundations).