One ounce equals 28.3495231 grams, based on the AskNumbers.com conversion chart. For a more precise conversion, 1 ounce converts to 28.349523125 grams, according to ConvertUnits.com.
For a more concise number, Metric Conversions.org rounds the numbers even further, calculating that 1 ounce equals 28.350 grams. Convertunits.com warns about rounding errors. Depending on the necessity for exact calculations, or whether estimates are acceptable, it can be beneficial to compare several online calculators. Special considerations must be given to the place value for each equation. While reducing the number of digits can create less room for error, rounded numbers give a less exact measurement.