:NPU = {0.16 × (24 hour protein intake in grams)} - {(24 hour urinary [[urea]] nitrogen) + 2} - {0.1 × ([[ideal body weight]] in kilograms)} / {0.16 × (24 hour protein intake in grams)}
ANPU closely related quantity, theand [[biological value]] (BV), is the percentage of absorbed nitrogen that is retained in the body.<ref name=EFSA2012 />{{rp|p=11}} NPU and BV both measure nitrogen retention, however,; the difference is that biological value is calculated from nitrogen ''absorbed'', whereas net protein utilization is from nitrogen ''ingested''.<ref>{{cite journal |last1=Hoffman |first1=JR |last2=Falvo |first2=MJ |title=Protein - Which is Best? |journal=Journal of sports science & medicine |date=September 2004 |volume=3 |issue=3 |pages=118-30 |pmid=24482589}}</ref> BVAnother closely related quantity is calculatedthe asnet postprandial protein utilization (NPPU), which is the productmaximum ofpotential NPU andof a dietary protein source under ideal digestibilityconditions.<ref name=EFSA2012 />{{rp|p=1112}}▼
NPU values can be either true or apparent, depending on whether the loss of endogenous nitrogen is taken into account or not; this is critical for precisely determining the efficiency of dietary protein utilization and the quality of different dietary protein sources.<ref name=EFSA2012 />{{rp|p=12}} The true NPU can be calculated as follows:<ref name=EFSA2012 />{{rp|p=12}}
▲A closely related quantity, the [[biological value]] (BV), is the percentage of absorbed nitrogen that is retained in the body.<ref name=EFSA2012 />{{rp|p=11}} NPU and BV both measure nitrogen retention, however, the difference is that biological value is calculated from nitrogen ''absorbed'', whereas net protein utilization is from nitrogen ''ingested''.<ref>{{cite journal |last1=Hoffman |first1=JR |last2=Falvo |first2=MJ |title=Protein - Which is Best? |journal=Journal of sports science & medicine |date=September 2004 |volume=3 |issue=3 |pages=118-30 |pmid=24482589}}</ref> BV is calculated as the product of NPU and digestibility.<ref name=EFSA2012 />{{rp|p=11}}
Another closely related quantity is the net postprandial protein utilization (NPPU), which is the maximum potential NPU of a dietary protein source when determined in optimal, controlled conditions in healthy adults. To determine the NPPU of a dietary protein source, true dietary protein nitrogen retention is directly measured in the postprandial phase using <sup>15</sup>N-labeled dietary proteins. This is done because the postprandial phase is critical for dietary protein utilization. The measurement of the immediate retention of dietary nitrogen following meal ingestion is a reliable way to assess protein nutritional efficiency.<ref name=EFSA2012 />{{rp|p=12}}
The [[Protein Digestibility Corrected Amino Acid Score]] (PDCAAS) is a more modern rating for determining protein quality, and the current ranking standard used by the FDA.
