Every formula. Every unit. Every rounding rule.
ConstrCalc® performs mathematically accurate calculations only on values the user enters. It does not modify user values, does not modify user-supplied rates, does not modify units, does not change formulas, does not generate hidden calculations, and does not generate fake calculations.
When you enter an area (default unit: ft²) in the Materials tab, ConstrCalc multiplies your area by these constants to produce the required quantity. If you want to override, use the Manual Entry section instead.
| Material | Multiplier | Unit | Reference (per 1000 ft²) |
|---|---|---|---|
| Cement | 0.4 | Bags | 400 Bags |
| Sand | 0.0816 | Ton | 81.6 Ton |
| Steel | 4.0 | Kg | 4,000 Kg |
| Bricks | 8.0 | Pcs | 8,000 Pcs |
| Aggregate | 1.35 | ft³ | 1,350 ft³ |
| Paint (2 coats) | 0.0025 | Gallons | 2.5 Gallons |
For each standard material: Cost = Required Quantity × Unit Cost.
For manual entries: Cost = Quantity × Unit Price.
For custom (additional) materials: Cost = Quantity × Unit Price.
For each labor category with time unit = hours:
Total Cost = Workers × Hours per Worker × Hourly Rate
For time unit = days:
Total Cost = Workers × Days per Worker × Daily Rate
The equivalent daily rate shown for hours input assumes an 8-hour standard day: Daily Equiv = Hourly Rate × 8. This is displayed only; it does not affect the total.
Total Cost = Rental Days × Daily Rate
Each entry is a direct sum. The user enters the cost; ConstrCalc sums them into a Total Legal Cost.
Subtotal = Total Materials + Total Labor + Total Equipment + Total Legal
Overhead Amount = Subtotal × (Overhead % ÷ 100)
Profit Amount = (Subtotal + Overhead Amount) × (Profit % ÷ 100)
Grand Total = Subtotal + Overhead Amount + Profit Amount
Cost per Unit = Grand Total ÷ Total Area (unit = ft² or m² per your selection)
Currency selection changes the display symbol only. Rates listed in the currency selector reflect approximate exchange rates for label display context, but ConstrCalc does not convert your entered values. Enter values in the currency you selected.
Displayed totals are shown to 2 decimal places for currencies with fractional units (USD, EUR, INR, etc.) and 0 decimal places for currencies without fractional units in common use (JPY, KRW, VND, IDR, HUF). Internal computation uses full precision — rounding is display-only.
The Location field in Project Info (Standard 1.0x, High 1.2x, Low 0.8x) is a reference label displayed alongside your inputs. ConstrCalc does not automatically multiply your entered rates by this value. If you want to bake a regional multiplier into your rates, do so explicitly at input time.
All inputs are stored in browser localStorage. No values are transmitted to a server. Export is a client-side operation. Only the Contact form transmits data.
Formulas above are stable. Any change ships with a versioned changelog entry — you'll see it here first.