Benefits calculator - Partner moving in

Hi first post.

Is there a calculator that can be used to determine if my partner and I would be entitled to any benefits/help?. This isn't very romantic but the realities have to be dealt with before my partner moves in with me.

My partner currently works 23 hours per week as she has a 5 year old child. As a result she then claims benefits to top her pay up to afford rent, living costs etc she gets something called Universal Credit?. The Childs father does not always pay maintenance and there is a reluctance from my partner to challenge him (not for this thread)

I work full time have a mortgage etc etc etc. After paying the bills etc I have little left over . Due to my working hours I am not available for the school run arrangements so my partner is planning to retain her 23 hours per week for the foreseeable future. In an ideal world she would increase her hours either in her current job, new job but that is easier said than done.

I understand that if my partner moves in with me then her current benefit entitlement will be reassessed against the household income. What I want to know is, is there a calculator we can use to see what this would look like? I understand that she may lose benefits when my wage is taken in to account.

Like I say not very romantic but you have to sometimes be realistic