Warren John Cowley took a hammer to a fight in a Dunedin boarding house, but it was he who ended up with 65 stitches, a fractured cheek bone and bleeding to his inner ear and eyes.

Both the 52-year-old man and the target of his anger, David Gerald Lange (34), were charged over the incident on April 7 last year.

It was somewhat ironic then, Judge John Macdonald told the Dunedin District Court this week, that the man who ended up worse off would end up in jail.

He sentenced Cowley to 12 months' imprisonment, whereas Lange got nine months' home detention when he came before the court in December.

The judge said he had no other choice but to incarcerate Cowley.

"This was an incident where you started it but the victim, in fact, finished it," he said.

The two men were living at a boarding house in Melville St and had both been drinking on the day of the incident, the court heard.

Lange walked into Cowley's room and was met with a barrage of abuse from the defendant.

He turned to walk away and but the defendant swung at him four or five times with a closed fist. None of the punches caused any damage. Cowley aimed a few more blows at Lange, hitting the younger man in the jaw and collarbone.

Cowley then retrieved a claw hammer from his room and brandished it at Lange.

"Unfortunately for you, the victim was younger and stronger physically, I suspect, and took the hammer off you,'' the judge said.

Lange's first couple of blows with the weapon knocked his assailant to the ground.

He then punched him a couple of times and smashed him once in the back of the head with the hammer.

Lange dropped the hammer and inflicted a few more blows with his fist, before returning to his room.

Cowley was admitted to hospital with severe head injuries but when police deduced the sequence of events, he was charged.

He pleaded guilty to assault and possession of a weapon. Lange had admitted a count of wounding with intent to do grievous bodily harm.

Judge Macdonald noted Cowley's 10 pages of convictions - many of which were for violence - and jailed him for a year.