How to calculate how many months in certain days?


Let’s say from 1st Jan 2021 until today is 294 days.
I have a price list for Machine A type rental is RM3,000/monthly.
I have a column calculated from 1st Jan until today written 294 days.
As you know 294 days is equal to 9 months, 21 days.
I need the calculation will be like
= (RM3,000 x 9months) + [ (RM3,000/31days) x 21days ]
= (RM27,000) + [ (RM3,000 / 30) x 21 ]
= RM27,000 + RM2,100
= RM29,100

That’s true if your rental starts on Jan 1.
But what if it doesn’t?
What if it starts on Jan 15, or April 27, or Jun 13, or any other date?
What would your calculation look like then?

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Yes because again i need to calculate the utilization but in Dollar perspective.
It was like RM3000 x 12 = RM36,000
We have potential to have RM36,000 in a year for Machine A.
Therefore, i have a number of days used as well.
Need to convert to month first.
What do you think?

I think it depends how you decide to define a month.
Let’s say for example that a rental starts on Jan 15.
You could do it two ways, either:

  • the first full month is until Feb 15, and on the 15th of each month thereafter, or
  • you do a pro-rata calculation until the end of Jan, and then full calendar months thereafter

I think the first option would probably be more common. But it’s up to you/your business to decide how to do it