[Secret_Ingredient]

I have 2 ounces of vegetable mass (cilantro) with a pH of 6.5. It is to be mixed (pureed) with 1 fluid oz. of 5% acetic acid (vinegar) which pH is 2.5 and 1 fluid oz. of water (theoretical pH of 7.0). The vegetable mass actually has a range of 5.5 to 6.5 but I am erring on the neutral pH side.

Could you please give the formula for finding the "average" pH of dilllution? I tried this URL, but got too confused:

http://rechneronline.de/chemie-rechner/ph-dilution.php

Otherwise I've been over the 'net a lot, but got lost.

[Borek]

Not enough information. While dilution of acetic acid is reasonably simple, cliantro contains plenty of substances that will have some - difficult to predict - buffering effect. The only viable approach is to mix and measure the pH, every estimate you can come with is not worth the electrons used to display the result.