Baseline is ~5 cups (60 oz) a day, based on the common clinical guideline of 30–35 mL of fluid per kg of body weight — for a 120 lb (~54.5 kg) person that's roughly 55–65 oz. That's lower than the often-cited general average for adult women (~91 oz/day total water, per the U.S. National Academies), which isn't scaled to body size.
Each pee-color check sets your goal for the next 24 hours, using the 8-point urine hydration color scale from hydration research (Armstrong et al., 1994): 1 (clear) → 2 cups, 2–3 (pale/straw, ideal) → 3 cups, 4–5 (dark yellow/amber, mild dehydration) → 4 cups, 6 (dark amber) → 5 cups, 7 (brown-amber, significant dehydration) → at least 6 cups, 8 (brown) → at least 7 cups.
This is a general wellness estimate, not medical advice. Urine color can also be affected by medication, supplements, or health conditions — if it's consistently dark, check with a doctor.