Estimate sandblasting time, abrasive media, labor and equipment cost, and total cost per area for a planned job.
Sandblasting Formula
The calculator works in two modes. Project mode estimates time, abrasive, and cost from surface area. Nozzle air mode sizes a compressor from nozzle and pressure.
- Area_base — raw surface area in sq ft (L×W for flat, π×D×L for pipe/tank outside)
- allowance — waste/overlap factor (0.10 typical, up to 0.20 complex)
- ProductionRate — sq ft per hour for the surface condition
- MediaUse — lb of abrasive per sq ft for the chosen media
- SurfaceFactor — multiplier for media consumption by surface (1.25 heavy rust, 0.65 wood, etc.)
- CFM_base — nozzle air consumption at 100 psi
- PressureFactor — scales linearly with pressure (0.62 at 60 psi, 1.20 at 120 psi)
- WearFactor — 1.0 new, 1.2 slightly worn, 1.5 badly worn
- 1.25 — reserve margin so the compressor isn’t run at 100% duty
Production rates and media use are field averages. Real numbers vary with operator skill, nozzle size, and air supply. Use the result as a planning estimate, not a fixed quote.
Reference Tables
Typical production rates and abrasive use by surface:
| Surface | Rate (sq ft/hr) | Contractor $/sq ft |
|---|---|---|
| Light rust / old paint | 75 | $2–$4 |
| Heavy rust / mill scale | 35 | $4–$8 |
| Concrete prep | 150 | $2–$3.50 |
| Wood restoration | 20 | $3–$6 |
| Fine detail | 15 | $6–$12 |
Nozzle air demand at 100 psi (multiply by pressure factor for other pressures):
| Nozzle | CFM @ 100 psi | Compressor (with 25% reserve) |
|---|---|---|
| 1/8 in (#2) | 20 | 25 CFM |
| 3/16 in (#3) | 45 | 56 CFM |
| 1/4 in (#4) | 81 | 101 CFM |
| 5/16 in (#5) | 137 | 171 CFM |
| 3/8 in (#6) | 196 | 245 CFM |
| 7/16 in (#7) | 254 | 318 CFM |
| 1/2 in (#8) | 338 | 423 CFM |
Worked Example & FAQ
Example: A 25 ft × 20 ft steel deck (500 sq ft) with heavy rust, blasted with coal slag, 10% allowance.
- Area_est = 500 × 1.10 = 550 sq ft
- Time = 550 ÷ 35 = 15.7 hours
- Media = 550 × 1.2 × 1.25 = 825 lb (17 bags)
- Contractor cost = 550 × $4 to $8 = $2,200–$4,400
Why does worn nozzle matter so much? A 1/4 in nozzle worn to 5/16 in passes about 70% more air at the same pressure. The compressor stays the same, so pressure drops and production falls. Replace nozzles when bore grows 1/16 in.
Does pressure really change rates? Yes. Dropping from 100 to 80 psi cuts production roughly in half. Hold 95–100 psi at the nozzle for efficient blasting.
How much abrasive should I buy? Round up to whole 50 lb bags and add a spare bag for setup loss and touch-ups.
