A 8mm TMT bar weighs 0.395 kg per metre, calculated with the d²/162.2 formula: (8 × 8) ÷ 162.2 = 0.395 kg/m.
A standard 12 m length of 8mm TMT weighs 4.74 kg (0.395 kg/m × 12 m).
Approximately 211 standard 12 m bars of 8mm TMT make one tonne (1,000 ÷ 4.74 kg per bar). Actual counts vary with rolling tolerance under IS 1786.