A 12mm TMT bar weighs 0.888 kg per metre, calculated with the d²/162.2 formula: (12 × 12) ÷ 162.2 = 0.888 kg/m.
A standard 12 m length of 12mm TMT weighs 10.66 kg (0.888 kg/m × 12 m).
Approximately 93 standard 12 m bars of 12mm TMT make one tonne (1,000 ÷ 10.66 kg per bar). Actual counts vary with rolling tolerance under IS 1786.