A 20mm TMT bar weighs 2.466 kg per metre, calculated with the d²/162.2 formula: (20 × 20) ÷ 162.2 = 2.466 kg/m.
A standard 12 m length of 20mm TMT weighs 29.59 kg (2.466 kg/m × 12 m).
Approximately 33 standard 12 m bars of 20mm TMT make one tonne (1,000 ÷ 29.59 kg per bar). Actual counts vary with rolling tolerance under IS 1786.