Note: The precision may be limited.
Just as a laboratory will calculate a carbohydrate value by subtracting fat, protein, fibre, moisture and ash from 100%, you can do the same for ash using NutriCalc.
The formula is:
% ash = 100 - % fat -% protein - % available carbohydrate - % fibre - % moisture
This does not apply when using Canadian and USA formats. Then the formula that should be used is:
% ash = 100 - % fat -% protein - % total carbohydrate - % moisture
Why may the precision be limited?
When subtracting large numbers from one another, leaving a small result, small errors in the larger numbers may have a significant effect on the result.
So if you use the above formula in this example:
% ash = 100 - 10.0 - 15.0 - 20.0 - 5.0 - 48.0, you get 2.0% ash.
But if all the values are 0.1% higher,
% ash = 100 - 10.1 - 15.1 - 20.1 - 5.1 - 48.1, and you get 1.5% ash.
However, ash values are usually required to fill in a space on a specification. In this case, the ash usually has no significance, except to ensure that the values add up to 100%.
One exception, however, is providing ash content for the labelling of animal foods. Because of the lack of precision, we do not recommend using nutrition calculation for ash content labelling of animal foods.