I've finished my long forgotten calculator which allows you to compare several nominal interest rates in one table. Rates are set through the annual interest rate and the interest accrual period. The effective interest rate is calculated by nominal interest and nominal period.
Effective interest rate formula
where j - nominal interest rate,
m - the number of interest accrual periods
Basically, it is clear that at the same nominal interest, the more often the accrual period, the more profitable the contribution is.