Rounding numbers in complex conditions in Excel formula

Question

I need to round up/down the numbers (last 2 digits, no decimal) based on three conditions:

1. if 00, then -1
2. if 01 to 49, then round up to 50
3. if 51 to 98, then round up to 99

examples:

• if the number is 1251, then it's 1299
• if the number is 1298, then it's 1299
• if the number is 4874, then it's 4899
• if the number is 1433, then it's 1450
• if the number is 1880, then it's 1899
• if the number is 1301, then it's 1350
• if the number is 1200, then it's 1299
• if the number is 1250, then it's 1250 (unchanged)
• if the number is 1299, then it's 1299 (unchanged)

..................

Answer 1

Try this. (Its quite nice apart from the fudge at the end for the 0 case):

=(CEILING(A1/50,1)*50)-IF(MOD(FLOOR((A1-1)/50,1),2)=1,1,0)

In explanation:

1. (CEILING(A1/50,1)*50) rounds up to the next 50
2. IF(MOD(FLOOR(A1/50,1),2)=1,1,0) takes off 1 if the number is large than an odd multiple of 50

Answer 2

assume value is in a1

=IF(MOD(A1,100)=0,A1-1,IF(MOD(A1,100)<51,A1+50-MOD(A1,100),A1+99-MOD(A1,100)))