Easy way to calculate tension difference for tuning down to D standard?

[Bassinga]

Not sure I can attach a PDF but D'addario has a string tension chart including the formula on Page 4 which is explained. It also lists the unit weights for all the D'addario strings on page 10.
https://www.daddario.com/globalassets/pdfs/accessories/tension_chart_13934.pdf

EDIT: fixed a mistake

 

[80jazz]

Based on the Stringjoy chart, it seems that 45-65-80-110 would get pretty close.

 

[iiipopes]

Yes, it depends on which way you are going. Dividing by 1.26 is about the same as multiplying by .79.

 

[garrett77]

Simplified formula for different tunings:
T ratio = 1/(1.0595^2N) for tuning down
T ratio = 1.0595^2N for tuning up
N = number of half steps

 

[fretlessman71]

This is a brilliant thread. I will have to peruse it once the caffeine and B12 starts working its magic in my system.

On a related but separate note, is there a way to calculate (this will be a toughie) how much you need to alter the action and neck relief if you choose to tune up/down using the same set of strings, but want to have the bass essentially play and feel the same?

IOW, if I tune my EADG bass down to DGCF, releasing tension on the truss rod will get the neck back to its previous shape, and raising the action will help to account for looser strings. But is there a formula for this?

 

[smurfco]

If only there were such a convenient way to calculate the tension in my marriage.