Can someone please give me a hand calculating Mash Efficiency manually? I use mostly Gladfield malt along with some cara 'x's' and BeerSmith 3 but would like to calculate manually so I have a grasp of what's going on.

Base recipe in Kilograms for 25 Litres wort:

American Ale malt (Gladfield) 5.5, CARAMALT 0.5 CRYSTAL LIGHT 0.3

The SG's I get from Beersmith are 1.037, 1.035 and 1.035 respectively.

I am not sure how to convert this to potential points for Kilograms and Litres before working out the overall mash efficiency. I think the first part of the calculation is just to multiply these together, which gives: 203.5 (5.5x37 etc.), 17.5 and 10.5. From here, I'm not sure what conversion Beersmith has used to gain their efficiency estimate. Can anyone assist? Cheers

1 Answer 1


To start with, I'd figure out the yield as a percentage. I find this number way more useful, especially as maltsters generally provide a yield as a percentage on their analysis sheets. To do this, divide the ppg of the grain by 46 (sucrose ppg). That gives you the percentage of the weight of the grain that will become extract.

e.g. 1.037 --> 37/46 = 80.4% or 0.804

Then multiply that by the weight of the grain to find out how much of the grain should become extract.

e.g. 5.5kg x .804 = 4.42kg extract

Do that for each grain, then add all the extract quantities together.

((37/46)x5.5)+((35/46)x0.5)+((35/46)x0.3) = total extract

Divide the total extract by the total wort weight (volume is close enough). That gives you your maximum gravity in Plato. In this case it's about 20 plato (20% extract by weight).

Now all you do is divide your actual gravity in plato by that number.

e.g. actual gravity 16 plato 16/20=80% efficiency

This may seem a bit foreign coming from a classic homebrew background, but after a little playing around, you will probably find that using plato makes a lot more sense if you want to understand the maths.

Hope that helps, feel free to ask for clarification.

  • Thanks very much! Now to figure out how to improve my efficiency lol.
    – W4K1NG
    Commented Aug 21, 2018 at 5:05
  • 1
    No worries! If you have any more plato questions, do hit me up. I'm a huge fan, and want to spread the love among homebrewers. I feel it demystifies the maths a lot, and leads to a better understanding of what's happening.
    – Frazbro
    Commented Aug 21, 2018 at 5:12
  • Is Plato the same as Brix up until a certain decimal point?
    – W4K1NG
    Commented Aug 23, 2018 at 1:54
  • Yes, they differ at about the 5th or 6th decimal place.
    – Frazbro
    Commented Aug 23, 2018 at 3:17

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