Use a divide by N counter....say like CD4040 to divide yr input signal and then take to microcontroller OR.. To avoid microcontroller , use CD4040 counter as divider , feed the divided output to Frequency to voltage convertor chip like NE565 PLL and display it using 3 1/2 digit ADC for display , the type used in DVM (ICL7137)......This division approach will allow you to feed input signal to very high RPM and still not jam yr circuit........I hope things are clear.........feel free to drop by in case of questions....