Formula on calculating month allocation per resource

So I am trying to find the most accurate way to write a formula that will calculate monthly allocation per resource. I am aware Smartsheet has Resource Management add-on but my company is not interested in purchasing that for the time being.

Instead, what I am trying to do is come up with a formula that calculates months based on start and end date and then the allocation I have divide it by the number of months. What I have so far is not really accurate because for 5% allocation, and a 2 month timeline the system is giving me 1 month. (see screenshot below - start date is beginning of April and end date is end of May - I want the month to be counted as 2 not 1 since there is definitely more days we're working on this task) Any thoughts?

I tried =([Target End Date]@row - [Target Start Date]@row) / 30

then I tried =([Target End Date]@row - [Target Start Date]@row) / 30.425 since I read this formula in another post here but not helping.

Lastly, I tried =MONTH([Target End Date]@row) - MONTH([Target Start Date]@row) which is what I'm using below but all of these are not as accurate as I want them to be.

Thanks

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