Grade Beam Calculator — m, m³, rebar
How to use this calculator
Enter the number of grade beams, the clear span, and the cross-section width and depth. Choose m, cm, or mm per field; volume, mass, bag counts, and bar lengths feed straight into your concrete order and rebar takeoff.
Cost — pick ready-mix per m³, 50 kg bags, or 25 kg bags. Select your currency below.
Reinforcement — longitudinal bars (top + bottom) plus stirrups spaced per EC2. Lap splices at 40db per EN 1992-1-1 §8.7.
Labor — rate per linear meter, per m³, or flat price.
Saved Calculations
| Time | Beams | Size | Vol m³ | Cost | Rebar m | Rebar | Labor | Total |
|---|
How to Use This Grade Beam Calculator (Metric)
Enter the number of beams and the clear span, then section width and depth, picking m, cm, or mm per field. Volume is net × (1 + waste): 5% for clean straight runs, 10% typical, up to 15% on layouts with many pier intersections. Switch the results between m³, litres, and 25/50-kg bag counts, and choose your currency for the cost panel. Concrete weight uses 2 400 kg/m³. For the piers or piles this beam spans between, use the concrete pier calculator, and for a continuous wall footing the strip footing calculator.
Reinforcement per EN 1992-1-1 (Eurocode 2)
Grade beams resist span and heave moments, so they are detailed as flexural members: continuous top and bottom longitudinal bars (Ø10–Ø20 here) with closed Ø8/Ø10 stirrups confining the cage. Maximum longitudinal stirrup spacing is 0.75·d (EC2 §9.2.2). Lap length is taken at 40·db per EN 1992-1-1 §8.7 as an estimating approximation; minimum cover is set by exposure class (25 mm XC1 up to 40 mm XD/XS). Bar masses: Ø8 0.395, Ø10 0.617, Ø12 0.888, Ø16 1.578, Ø20 2.466 kg/m; stock lengths 6 m or 12 m. For a pile-supported member with a deeper cage see the pile cap calculator.
Formulas
Volume per beam = Width × Depth × Length. Total = Volume per beam × Number of beams × (1 + Waste%). Bag count = ⌈m³ ÷ 0.024⌉ for 50-kg bags or ÷ 0.012 for 25-kg. Longitudinal length = (Span + laps × 40·db) × bars × beams × (1 + rebar waste). Stirrup perimeter = 2 × (Width − 2·cover) + 2 × (Depth − 2·cover); stirrup count = ⌈Span ÷ spacing⌉ + 1 per beam. For slab-on-grade tied to these beams use the concrete slab calculator; small bagged pours are sized with the concrete bag calculator.
FAQ
What size grade beam do I need? Light residential loads commonly use 30×60 cm; heavier loads or wider pier spacing use 45×75 cm or 60×90 cm. Depth is usually governed by span and frost/expansive-soil cover — these defaults are estimating starting points, so confirm the section and reinforcement with the project structural engineer.
Ready-mix or bags? At ≈0.024 m³ per 50-kg bag a single 30×60 cm × 6 m beam already needs about 60 bags, so ready-mix delivery is normally cheaper and more uniform for grade beams; reserve bags for minor patch volumes. When isolated column footings are also in scope, compare the spread footing calculator.
On pour day
Ready-mix in 2025 EU runs about €110–150/m³ delivered for C25/30, +€10–20/m³ for C30/37 freeze-thaw mixes — most plants charge a short-load surcharge of €40–80 under ~3 m³, so a single 30×60 cm × 6 m beam (≈1.1 m³) almost always triggers it unless you combine pours with the slab. The #1 estimator mistake on grade beams is under-counting laps: bars over 6 m (or 12 m stock) need a 40·db splice (≈640 mm for Ø16), and the calculator already adds one lap per bar but not corner hooks — add ~5% extra length for those. Keep cover per exposure class (25 mm XC1 to 40 mm XD/XS per EN 1992-1-1 Table 4.4N) and place spacers every 1.2 m so the bottom mat doesn't sink into the bedding during the pour.
