Concrete Beam Calculator — m, m³, rebar
How to use this calculator
Select beam type (rectangular, T-beam with slab flange, or L-beam edge). Enter beam width bw, total depth h, and clear span L using the mm/cm/m selectors. For T/L-beams, add flange width bf and slab thickness hf. Volume covers the beam stem plus the flange portion above the stem so you can order ready-mix or bags accurately.
Cost — pick ready-mix per m³, 50 kg bags, or 25 kg bags. Select currency.
Reinforcement — bottom tension bars, top compression bars, and stirrups with variable spacing per EC2 §9.2.2. Min/max reinforcement ratios shown.
Labor — rate per beam, per m³, or flat price.
Saved Calculations
| Time | Type | Size | Qty | Vol m³ | Cost | Rebar | Rebar | Labor | Total |
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How to Calculate Concrete for Beams (Metric)
Pick the section type, enter beam width, total depth and clear span in mm, cm or m, then set the beam count and a waste allowance (5% simple, 10% typical, 15% for congested cages or pump loss). Results give volume in m³, litres or 25/50 kg bag count, plus self-weight at 2,400 kg/m³ for crane and propping checks. For a single beam the concrete volume calculator or bag mix calculator is faster; for columns use the concrete column calculator.
Reinforcement per EN 1992-1-1 (Eurocode 2)
Bottom tension bars carry positive bending; top bars provide compression and continuity at supports. Links (stirrups) resist shear per §6.2 with longitudinal spacing limited near supports and opened up at midspan following EC2 §9.2.2. Minimum tension steel As,min = 0.26·(fctm/fyk)·bw·d but not less than 0.0013·bw·d — about ρ = 0.0014 for C25/30 concrete and B500B steel. Bar lengths include a 40·db lap (§8.7) plus end hooks; standard stock bar length is 6 m.
Formulas
Rectangular: V = b × h × L. T-beam / L-beam: V = bw × h × L + (bf − bw) × hf × L (stem plus flange above the stem). Self-weight = volume × 2,400 kg/m³. Stirrup perimeter = 2(bw − 2c) + 2(h − 2c) + hooks, with clear cover c = 30 mm. Effective depth d = h − c − Ølink − Øbar/2.
FAQ
What is the typical beam depth? A practical rule for simply supported beams is span/16 to span/12, so a 6 m span usually needs a 375–500 mm deep section. T-beam or rectangular? T-beams act monolithically with the slab, giving a wide compression flange — use a T-beam for interior beams and an L-beam at slab edges. Estimating walls or edge curbs instead? See the wall and curb & gutter calculators, or the concrete stairs calculator.
On pour day
Three line items estimators forget on beams. Minimum order surcharge — a single 6 m 300×450 beam is about 0.85 m³; most batching plants charge €60–120 below their 4 m³ minimum, so combine the beam with a slab pour or expect the short-load fee. Typical 2025 EU pricing is €110–160/m³ for C25/30 mix, €0.90–1.40/kg for B500B rebar, and €350–600/beam for forming + tying labour on residential work. Pump or crane skip — beams cast at ceiling level or inside congested forms need a pump (€500–900 minimum) — buckets do not work past 10 m of vertical lift. Lap splicing — under EC2 §8.7 a 40·Ø lap on a Ø16 bar is 640 mm, so a 7 m beam needs one splice per bottom bar — order 6 m stock plus splice pieces, not one continuous bar.
