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I've been building a spreadsheet to help predict OG for my brewdays. I know there are programs that can do the job but I like knowing the details behind the calculations. This brings me to a problem I've been having with calculating OG - When I use the ppg method my results align nicely to various brew calculators. However, when I use the metric system to generate plato my answer is very different and I'm unsure why.
Briefly. If I use 0.4536 kg (1 lb) pale malt in 3.785 L (1 g) with the specs of 80% extract and 37 ppg.
Via ppg this is 37 points * 1 /1 = 37 or 1.037 OG which is an accepted answer on online calculations.
Via metric we calculate
plato = 100*mass extract / (mass extract + mass water )
= 100*(0.4536 * 0.8) / ((0.4536 * 0.8) + 3.785)
= 8.75 plato or 1.0347 OG
If you double the mass of grain the variation is worse with Imperial 1.074 OG but Metric predicting 16.07 plato or 1.0657 OG
Am I getting the metric calculations hopelessly wrong?
Briefly. If I use 0.4536 kg (1 lb) pale malt in 3.785 L (1 g) with the specs of 80% extract and 37 ppg.
Via ppg this is 37 points * 1 /1 = 37 or 1.037 OG which is an accepted answer on online calculations.
Via metric we calculate
plato = 100*mass extract / (mass extract + mass water )
= 100*(0.4536 * 0.8) / ((0.4536 * 0.8) + 3.785)
= 8.75 plato or 1.0347 OG
If you double the mass of grain the variation is worse with Imperial 1.074 OG but Metric predicting 16.07 plato or 1.0657 OG
Am I getting the metric calculations hopelessly wrong?
