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.
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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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