What size chainsaw blade do I need?
I want to buy a chainsaw to chop up some trees in my yard for firewood. The trees are already down they just need to be cut. Any recommendations on a good (inexpensive) chainsaw that does a nice job cutting, and the best size blade that is needed?

It really depends on the size of the trees being cut. You don’t want to purchase a saw that is undersized and underpowered. However, you don’t need professional grade forestry model either. A 24 inch blade is your basic middle of the road size of blade; 18 inch blades are good for general maintanance projects around large acreages but fall a little bit short when it comes to cutting firewood.
As for manufactures, Poulan and Husqavrna(CQ?) are good quality manufactures; though I personally choose a Husky over a Poulan any day of the week. Husky’s are real durable chainsaws with good power.
poulan makes a pretty good chain saw that is not too expensive as far as length that should not matter much as long as you can buy blades to match 15 and 18 inches are usually the standard
It depends on the tree diameter I like an 18inch its the most versatile for most jobs smaller blades make it harder to get through tree trunks. Make sure you can handle it get some safety tips.
I have the 18" Craftsman and it works fine for this job.
Get some pointers from someone who has some experience.
Those saws cut real easy, until you make a mistake.
Then they can bite real hard.
Think each cut through at first.
Which way will the pieces fall?
Will they tend to grip the blade?