Ld is given by the formula
View attachment 2711
Where phi is the diameter of the bar
Sigma-S is the strength of the bar
Tbd as follows -
For M20- 1.2
For M25-1.4
For M30-1.5
For M35-1.7
For M40 and above-1.9
These Tbd values are for mild steel bars, i.e, Fe250
For HYSD bars, like Fe415 and Fe500 multiply the value given above by 1.6 (or in short we're increasing it by 60% as per codal recommendations)
Therefore, for your question
Sigma S is 415
Tbd is (1.6*1.2)
Plugging in these values into the formula we get the Development length as
Ld=54d
Or Ld=54*25=1350 mm or 1.35m
Hope it's clear.
P. S this formula is available in IS 456:2000,pages 42-43.
Regards.