Which wetsuit do I need?

So you want to know which wetsuit do you need. Before anyone can answer that question you will have to ask and answer yourself the following questions:

1. What is my sport? Do I need a wetsuit for surfing, diving, windsurfing, triathlon etc...
2. Where and when am I going to use it? Is it going to be summer, winter, cold water, warm water...
3. How much money am I willing to spend? Better wetsuits cost more, I think they are worth the money... but if you won't need it a lot, maybe a cheaper one is a better idea.

I cant answer or predict the first and third one for you, but I can give you a water temperature guide/chart for wetsuits. You can check this link or to sum it up here (the temperatures are water temperatures):

TEMP: > 77 F/> 25 C
You don't need a wetsuit

TEMP: 72F–77F / 22C-25C
If the the weather is colder wear a shorty. Or a wetsuit top maybe.

TEMP:68F–72F/20C–22C
Shorty. Or even spring suit/ 3/2 full suit in cold weather.

TEMP: 64F–68F / 18C–20C
Spring suit or full suit 3/2. 

TEMP: 59F–64F / 15C–18C
A good 3/2 full suit, 4/3 wetsuit is better.

TEMP: 54F–59F / 12C–15C
4/3 wetsuit+ booties, If you surf 54F a lot get a 5/3 wetsuits.

TEMP: 48F-54F/9C-12C
5/3 or 5/4/3 wetsuit + booties + gloves + hood.

TEMP: < 48 F / < 9 C
5/3 wetsuit is OK, 6/5/4 is better. Use THICK booties, gloves and hood (5mm or more).

Hope that helps.