Construction Labor & Duration Calculator

The labour and duration calculator answers the foreman's first scheduling question: with this many workers at this productivity rate, when does the job finish? Multiplying the productivity rate (units per worker per day) by the workforce size gives the daily output. Dividing the total work volume by daily output and rounding up gives the working days. Calendar days are then adjusted: Saudi sites typically rest Friday, so working days × 7/6 captures the lost day per week; an additional ~4% accounts for the ~15 paid public holidays per year (Eid Al-Fitr, Eid Al-Adha, National Day, Founding Day). Total cost is straightforward: working days × workers × daily wage.

Core formula

Productivity per day determines working days; calendar days adjust for rest days and holidays; cost scales with workers and wage.

Working Days = ⌈Volume ÷ (Rate × Workers)⌉ | Calendar Days = Working × 7/6 (Fri) × (1 + 15/365) (Holidays) | Cost = Working × Workers × Wage

Worked example — 500 m² of tile laying

Inputs: work volume = 500 m², productivity rate = 10 m²/worker/day, workers = 5, daily wage = 150 SAR, exclude Fridays = yes, exclude holidays = yes.

1. Productivity per day = 10 × 5 = 50 m²/day
2. Working days = ⌈500 / 50⌉ = 10 days
3. Calendar (Fri adj.) = 10 × 7/6 = 11.67 days
4. Calendar (holidays adj.) = 11.67 × (1 + 15/365) = 12.15 → ⌈⌉ = 13 days
5. Total labour cost = 10 × 5 × 150 = 7,500 SAR
6. If start = today, completion ≈ today + 12 days

Common mistakes to avoid

• Quoting calendar days as if they were working days — confuses the client and shortens the perceived schedule.
• Using an over-optimistic productivity rate — site reality is usually 70–80% of textbook figures.
• Forgetting that some holidays overlap with Fridays — the multipliers are independent and slightly overcount when they do.
• Not adjusting for inexperienced labour — first-time workers run at 50–60% of standard rates for the first week.

Tips for accurate estimates

• Saudi standard rates per worker per 8-hour day: tile laying 8–12 m², painting 25–30 m², block work 6–8 m².
• Add a 10–15% schedule buffer for site disruptions (rain, deliveries, inspections).
• When pricing for the client, quote calendar days plus a 10% buffer — round up to the nearest week.
• Track actual productivity on the first few days and re-baseline the estimate.