Ways of expressing agreement

These expressions will make your speech richer!!

That’s right/You’re right/I know: used when agreeing with someone:
‘It’s supposed to be a very good school.’ ‘That’s right. They get great results.’
‘He’s really boring, isn’t he?’ ‘Oh, I know, he never stops talking about himself.’

Exactly/Absolutely/I couldn’t agree more: used for saying that you completely agree with someone:
‘When we were young, people didn’t get into debt.’ ‘Exactly. You just bought what you could afford.’
‘I think Jacob is the best person for the job.’ ‘Absolutely. I’ll be amazed if he doesn’t get it.’
‘We had to wait three months to get a phone line – it’s ridiculous.’ ‘I couldn’t agree more.‘

You can say that again/You’re telling me: a more informal way of saying that you completely agree with someone:
‘It’s so cold outside!’ ‘You can say that again!‘
‘The buses are so unreliable!’ ‘You’re telling me! I’ve been waiting here for half an hour.’

Why not? used when agreeing with a suggestion someone has made:
‘Let’s go to the cinema tonight.’ ‘Why not? We haven’t been for ages.’

I suppose (so)/I guess (so): used when you agree that someone is right, but you are not happy with the situation:
‘We’ll have to get some new tyres.’ ‘I suppose so/I guess so. But it will be expensive.’

Source: Macmillan