This is the formula that i use to stake on my ratings top 3.

(0+60)/a1
(0+60)/a2
(0+60)/a3

where a1 a2 a3 are the odds. All loses are added to the target.

I'm trying to make a profit of $50. Someone might be able to improve the formula. Any suggestions.

What is that formula doing?! Why do you do 0 + 60? Why not just start with 60?

Anyway what you want to do is this...

50/(odds-1)

Where you want to make $50 profit (i.e not including your stake). So if it was a 1.50 horse you'd stake $100 (50/0.5). A $10 horse and you'd only need to stake $5.56.

Can I use it for the top 3 horses and make $50 proit no matter which one wins.

Aaaah ok you want to dutch your top 3 to make $50 profit if any of them win. Right well thats a little more complex and requires several forumals...

It's a multi-step process.

1) Find the probability of each runner. This is just 100/odds. Eg a 2.0 runner = 50% probability.
2) Sum the probablity for each of the runners (it should/must be less than 100).
3) Calculate the "advantage" in your favour(100 - total probabilty from step 2)

Then for each runner you can plug in this formula...

(100/Odds)*(50/advantage)

Let's take this formula one step further and use it for sports betting, especially 2 team multi bets to see if there is an advantage.

No advantage - no bet.