What is the difference about gue

When you speculate, you are usually thinking of different things that might be possible or that might happen, based on facts you already know.

He watched a lot of game shows, and speculated about ways to win money.

The economy was bad because of bankers speculating on the stock market.

To guess is to try and get a correct answer without knowing for sure.

He guessed his height was six feet, but he hadn't measured himself.

I didn't study for the test, so I guessed the answers.

She couldn't remember what time they were meeting, so she guessed noon.

Guess can also be used as a noun, but speculate can't.