Full and partial eligibility for cap gains on home sale

I have lived in my house for 15 years, I got married and now my wife has lived in the house for 1 year. If we sell now, I get $250k exemption on cap gain. Since my wife has only lived in the house for a year, we can't get another 250k exemption, but is there a way to get a partial exemption for the year she lived here? Is it prorated?