Quick conversion factors for the units encountered daily on Indian sites — switching between SI (kN, MPa, m), CGS (kg, cm), and old FPS units (lbs, ft, psi). Useful when reading old IS codes, imported drawings, or US/UK specifications.
Force
| From | To | × Factor | Note |
|---|
| 1 kN | kg | 101.97 | Round to 100 kg for site work; exact 1 kgf = 9.81 N |
| 1 kN | tonne (mt) | 0.102 | 1 tonne ≈ 9.81 kN |
| 1 kN | lbf | 224.81 | Pound-force |
| 1 tonne (mt) | kN | 9.81 | Often rounded to 10 kN on site |
| 1 kg | N | 9.81 | g = 9.81 m/s² |
| 1 N | dyne | 100,000 | CGS legacy unit |
Stress / Pressure
| From | To | × Factor | Note |
|---|
| 1 N/mm² (MPa) | kg/cm² | 10.197 | Round to 10 — used everywhere on Indian sites |
| 1 MPa | kN/m² | 1000 | 1 MPa = 1000 kPa |
| 1 kN/m² | kPa | 1.0 | Identical units |
| 1 MPa | psi | 145.04 | Pound per square inch (US/UK) |
| 1 kg/cm² | psi | 14.22 | Old FPS |
| 1 bar | kPa | 100 | Atmospheric pressure ≈ 1 bar |
| 1 bar | kg/cm² | 1.02 | Approximately equal |
| 1 mWC | kPa | 9.81 | Metres of water column — for plumbing/hydrostatic |
Length
| From | To | × Factor | Note |
|---|
| 1 m | ft | 3.281 | Foot |
| 1 m | in | 39.37 | Inch |
| 1 ft | mm | 304.8 | Round to 300 mm (architectural module) |
| 1 in | mm | 25.4 | Exact |
| 1 yd | m | 0.9144 | Yard |
| 1 mile | km | 1.609 | — |
| 1 chain | m | 20.117 | Land surveying (Gunter's chain) |
Area
| From | To | × Factor | Note |
|---|
| 1 m² | ft² | 10.764 | Square foot |
| 1 m² | yd² | 1.196 | Square yard |
| 1 ft² | m² | 0.0929 | — |
| 1 hectare (ha) | m² | 10,000 | 100 m × 100 m |
| 1 acre | m² | 4046.86 | ≈ 0.405 ha |
| 1 acre | ft² | 43,560 | — |
| 1 cent | m² | 40.47 | South India / Kerala land unit (1/100 acre) |
| 1 ground | ft² | 2400 | Tamil Nadu land unit |
| 1 bigha (UP) | m² | 2530 | Varies by region — UP/Bihar standard |
| 1 katha (Bengal) | m² | 67 | Varies by region |
Volume
| From | To | × Factor | Note |
|---|
| 1 m³ | ft³ | 35.31 | Cubic foot |
| 1 m³ | yd³ | 1.308 | Cubic yard |
| 1 m³ | litre | 1000 | — |
| 1 ft³ | m³ | 0.0283 | — |
| 1 cement bag | m³ | 0.035 | 50 kg bag, density 1440 kg/m³ |
| 1 brass (sand/agg) | m³ | 2.831 | 100 ft³ — Maharashtra/Gujarat unit |
| 1 ton (cement) | bags | 20 | 1000 kg / 50 kg |
Density / Unit Weight
| From | To | × Factor | Note |
|---|
| 1 kN/m³ | kg/m³ | 101.97 | Round to 100 |
| 1 g/cc | kg/m³ | 1000 | — |
| 1 g/cc | kN/m³ | 9.81 | — |
| 1 lb/ft³ | kg/m³ | 16.018 | — |
Engineering Quick Ratios
| From | To | × Factor | Note |
|---|
| Cement bag weight | — | 50 kg | Standard Indian bag |
| Cement density | — | 1440 kg/m³ | Bulk density of bagged OPC |
| Steel density | — | 7850 kg/m³ | Mild & high-tensile steel |
| Concrete (RCC) | — | 25 kN/m³ ≈ 2500 kg/m³ | — |
| Rebar weight | kg/m | D² / 162.2 | D in mm |
| Brick (modular) | — | 190×90×90 mm | IS 1077 |
| Brick (standard) | — | 230×115×75 mm | Older / regional |
Notes
• Indian sites mix kg/cm² and N/mm² freely — remember 1 N/mm² ≈ 10 kg/cm² (exact: 10.197)
• Always include units in calculations — 'g (gravity) = 9.81' is the most-forgotten conversion
• When reading drawings imported from US/UK firms, ksi is common: 1 ksi = 6.895 MPa
• Old IS codes (pre-1980s) used FPS — be cautious converting old design tables
• 1 sq ft is the default unit on most Indian property listings — 1 m² ≈ 10.76 sq ft
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