Brewer's friend priming calculator says 1.25 volumes after aging and 3.4 with the amount of priming sugar I used.

*edit - and maybe not quite that bad according to @doug293cz, who is probably a good deal more reliable than some random online calculator.*

edit 2 - I was shooting for ~3 volumes because a) it's a Belgian, b) I had bottles that can handle it, and c) my last few batches have all been under-carbonated when shooting for ~2.5 volumes.

I looked at the Brewers Friend Priming Calculator, and they use this polynomial to calculate residual CO2 volumes post fermentation (which assumes 0 psi gauge pressure):

Volumes = 3.0378 - (0.050062 * temp) + (0.00026555 * temp^2)

I use a formula recommended by A J deLange (link to paper broken, but paper attached below.) The formula is:

Volumes = (Pressure + 14.695) * (0.01821 + 0.090115 * exp ( - (Temp - 32) / 43.11)) - 0.003342

Where for both cases temp is in °F, and pressure is in PSI gauge. The deLange paper gives max error for its formula as -0.044 volume, and RMS error at 0.01 volume, so it's pretty accurate.

I charted the outputs of the two formulas below, and the error in the Brewers Friend formula looks to be much worse than the deLange formula.

Also, I had to set the temp to 48°F in Brewers Friend to come up with a residual CO2 level of 1.25 volumes.

Brew on