I prefer to work with ratios (odds). Gut shot draw is 4 good cards to 43 bad, so almost 11 to 1 against hitting it.

If the pot was $5 and your opp makes a weak bet of $0.50, you'd have pot odds to call it. Divide the $5.50 now in the pot by the $0.50 to call and you get 11.

I'm constantly doing this on the fly, dividing the pot by cost to call to come up with the pot odds. I think being able to do this, counting outs, and knowing your odds to hit are crucial skills to develop.