I agree with Vanae G. and also suggest just ignoring the hit by turning and walking away.
Also know that his is normal and all kids go thru this stage. They haven't yet learned acceptable social skills so that they can express their frustration in more positive ways. At some point, when he's able to understand, you'll want to remind him to use his words.
Another way to handle it is with warmth and understanding. Calmly and gently hold his hand and tell him that hitting hurts; that we don't hit in this house. Of course that does mean that no one else hits either. If hitting is acceptable some of the time it will be impossible to stop your 1 yo from hitting. His brain is not developed enough to be able to determine when hitting is OK and when it isn't.
Sympathize with him. Tell him you know he's frustrated, angry, whatever and say that even tho he's feeling that way hitting is not acceptable. You can then do one of two things depending on his response. Sometimes my grandchildren at that age would calm down and wanted to be held. I held them. Other times they would still be angry. In that case I walked away before they could hit me again. I'd tell them, when you're calm we can talk/play/etc. If he's tired and it's too late for a nap, arrange for some quiet time with him. Perhaps read him a story, play some soft music, or just rock him for a little bit. If he's hungry give him a snack even if it's close to meal time.
At times both I and my daughter, feed the child, and put him to bed early. We do the same thing for ourselves when we're tired and cranky and there is someone to take care of the kids. There is just no sense prolonging the misery.
I would do my best to see that he rarely skips a nap and that he has a regular routine around naps and eating. Hunger also causes kids to be cranky. Adults, too. My work partner would respond to my crankiness by suggesting that we stop and get something to eat. lol
What is important is letting your little one know that he's having a hard time and that you sympathize but you won't let him hurt anyone including himself. His feelings are OK. Hitting is not.
He doesn't yet have words for his feelings but you can begin giving him those words by saying something like, you're angry because I took that toy away. then don't try to explain why you took it away. That is too many words. What you want him to begin learning is that the way he's feeling is angry and that hitting because of feeling angry is not OK. You also want him to learn that you are in control of your own feelings and will not get angry in return. He needs to know that you understand and still love him.