How to calculate amount needed to get to max percentage

[mtthplysr]

Hi everyone,

So I am working on an excel sheet for my investments. What I would like to calculate is how many assets I need to buy to have the transaction costs be max. 2% of the total sum.

I can do it the other way around, lets say:

50 euro Asset = X

4 euro transaction costs = Y

2% max costs = Z

(1*Y)/X=29%. 

So I'd like to know how may of X I need to buy to bring the 8% down to two in this case. If you could help me with a formula that would be great. 

Thanks in advance!

[#2 · Accepted solution]

@mtthplysr Not sure about your maths as a transaction cost of 4 on a purchase of 50 equals 8%. Not 29%. But perhaps I have misunderstood.

If you now want to limit the cost %, you can use a formula like:

Y / max % / X = n

Used in your example that would be 4 / 0.02 / 50 = 4.

To check it, buy 4 at 50 = 200. Cost % = 4 / 200 = 2%