Formula & sources
Food water (mL) ≈ eaten grams × label moisture/100. Eaten mass is the whole portion, the chosen percentage, or the amount served minus leftovers. Sum all foods and add only extra water actually consumed. Use as-fed Moisture (max), not a dry-matter value. One food ounce is 28.3495 g, not a fluid ounce.
- Cornell Feline Health Center: HydrationDietary water and feline hydration.
- FDA: Complete and Balanced Pet FoodAs-fed moisture and food-label context.
- AAFCO: Reading Labels — Moisture and Calorie ContentGuaranteed-analysis moisture is a maximum.
- Purina US label: Fancy Feast Classic Chicken FeastThe 78% moisture example comes from this product label.
- NIST: SI Appendix B.8 Conversion FactorsFood-weight and US-volume conversions.
Reference values & examples
- Wet food example
- 78% maximum moisture
- Dry food context
- 10–12% moisture
- 1 food ounce
- 28.3495 g
- Half a portion
- 50% of estimated food water
- Added water
- 1 mL adds 1 mL
A 3 oz portion weighs about 85 g. At a label maximum of 78% moisture, the estimated water is 66 mL. For a mixed meal, 200 g at 78% plus 30 g at 10%, with 20 mL of added water consumed, gives an estimated total of 179 mL.
Common questions
How much water is in a 3 oz portion at 78% moisture?
An estimated 66 mL if the whole portion is eaten. Food ounces measure weight; 78% Moisture (max) is a label maximum, not a measured value for that meal.
How do I account for leftovers and mixed foods?
Add each food separately with its own moisture percentage. Choose the portion eaten or enter leftovers. Count added water only if consumed.
Does matching meal water also match nutrition?
No. Equal estimated water does not mean equal calories or nutrients. This tool compares label-based meal-water estimates; the daily-water tool compares a complete day with a total-water reference.