If a product that costs me $100 to make and I want to make 25% profit on it so I sell it for $125, later on, the cost of raw materials and production decreases by 20% but I still want to sell it for $125, in that case, what is the % of profit? 

In other words, I want to keep the final selling price unchanged, but the actual cost of the product decreases, how to calculate the profit %? Of course, $100 is just a number for illustration. I have many different numbers for real. Is there a general formula for that? Then I can apply more quickly.

1 hour ago, kenny1999 said:

If a product that costs me $100 to make and I want to make 25% profit on it so I sell it for $125, later on, the cost of raw materials and production decreases by 20% but I still want to sell it for $125, in that case, what is the % of profit? 

Does $100 represent total production costs (materials, labor and payroll, property and overhead, shipping, insurance, taxes, etc.), or does it represent only your raw materials costs?

If the first, then you don’t have enough info to answer.

If the second, then your 20% drop in costs results in your profit going from $25 instead to $45. That represents a 56% profit (up from the original 25% profit earned with the higher materials costs).