Conversion between inHg on gauge and kPa on MAP sensor

[capri_turbo]

I think this is in the correct forum. Forgive me if it isn't.

What I'm trying to do is produce a starter 3d map from my distributor curve. The thing that has given me a headache is transposing the vacuum figures given by my gauge to the kPa figures that the map sensor will reference.

I think I have figured it out, but would like a second opinion.

What I have so far is this:

At sea level, my vacuum gauge reads 0inHg and the MAP sensor should read 100kPa.

To calculate kPa from inHg we multiply by 3.386389, so 5inHg is 16.934kPa... however as the MAP sensor is giving 100kPa at 0inHG (gauge), I take it that the true reading on the map sensor is 100- 16.934 = 83.066kPa

So calculation looks something like this:

map reading (kPa) = 100 - (gauge reading inHg x 3.386389)

Have I got this correct? As yet I don't have an MJLJ to test this... I'll be building it later in the year. I do have a vacuum gauge to use at the moment and I'm trying to get figures from my existing setup for vacuum advance etc. whilst I have access to the gauge, to create a "starter" map based on the current distributer settings, which while not ideal, are safe.