‚ÄčAn important warning about calculators
We have sourced a variety of calculators we believe are reliable and will be useful to you.  
We do not, however, warrant their accuracy or their suitability to your particular needs or circumstances.

As with any tool which does calculations "garbage in" produces "garbage out" so use the results with care.  You need to understand the limitations of the results and the assumptions used and we strongly suggest that you use the tools as a precursor to seeking advice from us rather than "as advice".
Please also refer to the warning below