8x1 LED bar

Using Arduino LEDs and Multiplexing
5

This code generate no errors at compilation time:

  //LEDS
if (cm <=3 && cm>1){
broj = B11111111;}
else { if(cm>100 || cm==0){
broj = B00000000;}
else { if(75<cm && cm<=100){
broj = B00000001;}
else { if(50<cm && cm<=75){
broj = B00000011;}
else { if(30<cm && cm<=50){
broj = B00000111;}
else { if (15<cm && cm<=30){
broj = B00001111;}
else { if(10<cm && cm<=15){
broj = B00011111;}
else { if(5<cm && cm<=10){
broj = B00111111;}
else { if(3<cm && cm<=5){
broj = B01111111;}
}}}}}}}}

As your approximation looks close to square root for me, better way would be: cm = sqrt ( cm * 0.5 ); May be you could try with different coefficient (0.5), "squeezing" cm to 0-7 range you can use barGraph example in arduino IDE.