Am I calculating MPG correctly?

[YarisBlazer]

Ok, this is the second time I've tried to figure out my MPG; I want to make sure I am doing this right; this is how I calculate it:

Odometer reading now minus odomter reading at last fill-up divided by amount of gas I put in tank at this fill-up

Of course I always fill it all the way to full

I just filled up so today's equation is:

2623 (Odometer reading now at fill-up)
- 2262 (Reading at last fill-up)
____
361 divided by 11.551 gallons = 31.252 MPG

Is this right? I am doing mostly city driving so I would like to get this up to at last 36 MPG if I can; I'm in Florida so must run the A/C while driving.

Thanks for any input; my last reading was 32 MPG.