Formula field issue - wrong result

Question

We have a formula field that calculates savings percentage. The formula is as below, ROUND((( Total_Saving__c * 100) / Total_balance__c ),2) where total saving is also a formula field, the formula for total saving is as below, Total_balance__c - Required_Amount__c and the total balance is a currency field.

And we are getting the results as follows

Total savings = 287.20

Total balance = 1187.20

Savings percentage = 24.19

But if we do the reverse calculation and calculate 24.19% of 1187.20 on a calculator, the result is 287.18. so there is a difference of 0.2. I am not able to identify the issue in the formula field.

Answer 1

The actual savings percent is 24.19137466307278% (at least as far as my calculator can go), leaving to a difference of 0.0013746630727763%, which leads to a difference of 0.01632, which when rounded to two decimal places results in the difference of 0.02 that you've observed. Never underestimate how even a very small fraction of a percent can result in relatively large rounding errors. If you're using rounding at all, you can almost always expect at least a 1-2 cent difference, no matter how you do the math. That's just how rounding works.

Answer 2

Actual saving percentage is actually having more than two decimals.

287.20 / 1187.20 = 0.24191374663072776280323450134771 (24.191374663072776280323450134771%)

But your reverse calculation is only taking two decimal places:

24.19% * 1187.20

The difference is:

0.00001374663072776280323450134771 * 1187.20 = 0.01632 (0.02)

Using ROUND() function in your formula is unnecessary because you have the option to specify the number of decimal places for the field.