I would like to ask a general question on how you would calculate the product consumption/product sales ratio, yearly and monthly.

The approach I followed is the one described below:

Let’s set 2025 as an example for that I used the following formulas:

**Yearly Ratio 2025 **= (End Stock Dec-24 + Total Product Sales 2025)/Total Product Consumption 2025

Monthly Ratio through 2025 (the same for each month)
**January 2025: **(End Stock Dec-2024 + Product Sales Jan-25)/Product Consumption Jan-25
**February 2025: **(End Stock Jan-2025 + Product Sales Feb-25)/Product Consumption Feb-25

I wanted to calculate the monthly ratio to see when my stock is gonna start to decrease and plan some orders in advance to avoid running out of stock. My problem comes cause the monthly ratios that I got are way higher when I compared to the yearly ratios and therefore I cannot see/estimate when I am gonna run out of stock. However, the yearly ratio is really low and sometimes indicates that I will run out of stock even though it is not reflected on the monthly ratios

I think it has to do with the fact that on the yearly ratio I didnt consider the accumulated stock in 2025, but I still cannot figure out a formula to gather all of this

I would appreciate some help

Thanks!
Silvia