Jack is 7 feet tall and John comes up to his chest only.

[tufguy]

1) Jack is 7 feet tall and John comes up to his chest only.
2)John is chest high to Jack.

Please check my sentences.

 

[tedmc]

2) John's height is at John's chest level.

 

[5jj]

1) Jack is 7 feet tall and John comes up to his chest only.
2)John is chest high to Jack..

2) John's height is at John's chest level.

None of these is particularly natural. try:

Jack is 7 feet tall; John comes up only to his chest.

 

[emsr2d2]

2) John's height is at John's chest level.

John and John?!

 

[tufguy]

John and John?!

I am sorry. "John comes up to Jack's chest".