Water expansion is quite strange Aces. It is a logarithmic curve except at very low temperatures.
In your BIABacus, go to the second sheet called, "Unit Conversion." On the right hand side you will find a 'Water/Wort Expansion and Contraction" section on the right hand side.
The co-efficients we use are from, "Brewing Science and Practice," by Briggs, Boulton, Brookes and Stevens. We use the following numbers...
Ambient: 5.0 C (41.0 F) = 0.99999
Mash: 65.0 C (149 F) = 0.98059
Boil: 100 C (212 F) = 0.95838
The ambient co-efficienct is fine to use at all your low temperatures such as for conditioning through to pitching temps.
The mash co-efficient is fine to use for all your mash and sparging temperatures and for your hot water.
The boil co-efficient should only be used very close to boiling point.
The BIABAcus uses the above co-efficients as follows...
1.000000 Volumes at ambient temperatures becomes 1.019784 volumes at mash temperatures and 1.043417 volumes at boiling.
In addition to this sheet, on the first sheet of The BIABacus, '[Hot] Strike Water Needed (SWN) in Section K, will also give you what you are looking for. Finally, Sections S and T will tell you the depth and headspace of the wort at the relevant brewing stage with the temperature factored in. These two sections can also be set up so as they will work accurately for kegs.
In other words, the BIABacus does all the work for you.