"मेरे नाना अस्सी साल के हैं।"

अनुवाद: My grandfather is eighty.

[AshKnth]

I think
"My grandfather is eighty years old" is also correct.

[jitengore]

Yes, it is an acceptable translation now.

[JoshiDinesh]

My Grand Father is eighty years old

[jitengore]

"Grandfather" is a single word (it is a compound word).