91 Days BCR (Bangladesh Compounded Rate) is a daily rate based on the cut-off yield of 91 days Treasury Bill auction. This is a reference rate which will be primarily used to set the rate of floating rate instruments of government. The following formula is applied to calculate the rate:

Where
C = The compounded rate expressed as an annual rate
d = The number of days over which to compound (i.e. 91 days)
r_i = The cut off yield of 91 days treasury bill set in auction
D = The day-count convention (e.g. 365 days)