How is the Fuel Moisture Content (FMC) percentage calculated?

• A. (Wet Weight - Dry Weight) / Dry Weight × 100
• B. (Dry Weight - Wet Weight) / Dry Weight × 100
• C. (Wet Weight + Dry Weight) / Dry Weight × 100
• D. Wet Weight / Dry Weight × 100

Answer: (A)

Fuel Moisture Content is the amount of water in the fuel expressed as a percentage of its dry weight. To get it, you compare how heavy the fuel is when it’s wet (Ww) to when it’s completely dry (Wd). The water portion is Ww − Wd, and dividing that by the dry weight (Wd) and multiplying by 100 converts it to a percent: FMC = (Ww − Wd) / Wd × 100. For example, if the wet weight is 4.0 g and the dry weight is 3.0 g, the water is 1.0 g and FMC = 1.0 / 3.0 × 100 = 33.3%. The other forms either don’t represent water relative to dry mass, add weights, or omit the reference to dry weight, so they don’t yield the correct FMC.