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Shotcrete Quantity Calculator

Back-calculate batched volume and material use from rebound.

Quick answer

With the default inputs: Area 100 m² · Design thickness 100 · Location Side wall etc.Concrete to batch 11.76 m³

Edit the inputs below to recalculate.
SubstrateDesign thickness mm
Thickness is the design layer; the actual mix must be multiplied by a 1.2-1.5 rebound factor, because material that bounces off is still bought.

Inputs

m²
kg/m³
kg/m³

Result

Concrete to batch
11.76m³
Design volume (net)10.00m³
Rebound rate15%
Volume lost to rebound1.76m³
Batched mass27.1t
Cement required4.94t
Material wasted4.1t

Rebound is empirical: 10-20% on side walls, 20-30% at the crown, more overhead. It depends on nozzle distance (typically 0.8-1.2 m), incidence angle (perpendicular is best), w/c ratio and grading. Note the design volume is net section while batching must cover rebound - this is the main reason shotcrete costs far more than ordinary concrete. Rebound must never be reused.

Formula

Net volume = area × thickness
Batch = net ÷ (1 − rebound)rebound is a loss, so invert
Cement = batch × cement per m³
Loss = batch − net
Side wall 100 m² at 100 mm with 15% rebound: net 10.00 m³ but 11.76 m³ must be batched, so 1.76 m³ (about 4.05 t) is lost to rebound; at 420 kg/m³ that is 4.94 t of cement.

How to work it out

  1. Net in-place volume = sprayed area × design thickness.
  2. Set rebound by location: 10-15% for walls, 15-25% for the crown, 20-30% for invert or overhead work. Rebound is the only empirical input here and the largest source of error.
  3. Mixed volume = net volume ÷ (1 − rebound). It is a division, not an addition: spraying 100 m³ at 20% rebound leaves 80 m³ in place, so 125 m³ is needed.
  4. Consumption follows the mixed volume: cement, sand, stone and accelerator each scale from it.
  5. Accelerator dosage is usually 3-5% of cement weight; wet spraying uses less than dry, but the plant costs more.

Where it goes wrong

Material and cost

Wet-mix sprayed concrete runs 550-850 per m³ all in (labour, plant, accelerator, rebound), dry-mix 450-700 with higher rebound and dust. Every 5% cut in rebound saves 40-70 per m³.

On site

Basis

FAQ

Why is crown rebound so much higher than side wall?
Gravity. On a wall the material sticks on impact; overhead it must overcome its own weight, and coarse aggregate falls away first. Crown rebound is typically 1.5-2 times the wall value and is richer in coarse aggregate, which leaves the in-place layer sandier and weaker. Hence the requirement for lifts of 70-100 mm at the crown.
Can rebound be reused?
No. It has lost water, picked up dust and fines, and its grading is destroyed (coarse-heavy, fine-poor), so reusing it cuts strength and durability - codes prohibit it. Clear it promptly and treat rebound rate as a process KPI: every 5 points of rebound saved is over 5% of material cost.
How much do nozzle distance and angle matter?
A lot. Rebound is lowest at about 1 m with the nozzle perpendicular; at 2 m or 45 degrees it roughly doubles. Air pressure must match too - too low and the stream cannot compact, too high and aggregate bounces. Much of the on-site quantity variance is nozzle technique and air pressure, not mix design.

Cite this page

Use this format in reports, method statements or coursework. The link is permanent.

Building Calculator. Shotcrete Quantity Calculator. 2026-10-25. https://jianzhujisuan.com/en/shotcrete-quantity

Results are estimating aids only and are not a design basis. Construction and final accounts must follow the drawings, the applicable standards and an approved method statement. Anything affecting structural safety, shoring or falsework must be checked by a suitably qualified engineer.