The first place to go to calculate what you can borrow would be one of the many trusted websites offering valuable mortgage tools. There are many mortgage calculators on the web from basic ones that will just multiple your income by industry averages to give you a figure and there are other sources offering more comprehensive mortgage calculators that will take other factors into account to give you a more realistic number.
If you wish to borrow money for a mortgage with a partner this can also be taken be calculated. There are many resources on the internet to give you estimates as to how much you can borrow. However while these will give you a rough idea as to what you can borrow you seek professional advice for a personalized evaluation.
There are many qualified individuals that you can seek advice from. I would recommend using the services of a mortgage broker. A broker can give you a clear idea of what you can afford; an experience one will know the current market rates and after a meeting to understand your circumstances will know what amount you will likely be offered by lenders.
Mortgage brokers have many other benefits other than their many role of arranging a mortgage which can be very beneficial to consumers especially if they search the whole of the market to find a lender that will calculate mortgage borrow for you that best suits your circumstances. Getting a recommendation for a friend of family will pay dividends as a good mortgage broker can be very supportive as you go through your mortgage application.
If you want to simply calculate mortgage borrow available for you and your partner there are many mortgage brokers who offer their service with no broker fees so there is no obligation to proceed with your application if you aren’t ready or not happy with the current mortgage broker. As you have probably understood I think mortgage brokers are of huge benefit to everyone whether you are just enquiring about a mortgage or are looking to get your first home/remortgage.