Free Tools
Pregnancy Water Intake Calculator
Your daily hydration goal from weight, trimester, and activity — the same engine as the ProbaBaby iOS app.
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How this works
Proper hydration supports amniotic fluid, nutrient delivery to your baby, and helps prevent common pregnancy issues like constipation and urinary infections. This calculator turns that need into a concrete daily number built from three things you already know: your weight, your trimester, and how active you are.
Set your weight on the slider — in kilograms or pounds, whichever you prefer. The baseline is 30 ml of water for every kilogram of body weight, so a heavier body starts from a higher target. If you enter pounds, we convert with the exact factor (1 lb = 0.45359237 kg) before doing any math.
Then pick your trimester and activity level. Pregnancy adds a growing bonus on top of the baseline — +300 ml in the first trimester (weeks 1–12), +400 ml in the second (weeks 13–26), and +500 ml in the third (weeks 27–40). Movement adds more: nothing extra if you are mostly sedentary, +500 ml for moderate activity, and +1,000 ml for an active lifestyle.
The result updates instantly as you move the controls, in the unit that matches your weight input: milliliters if you chose kg, US fluid ounces if you chose lbs. To make the goal practical, we also translate it into 250 ml cups and 8 oz glasses per day, and a breakdown card shows exactly how much of your total comes from weight, trimester, and activity.
The math behind it
The full formula is: daily target (ml) = weight (kg) × 30 + trimester bonus + activity bonus. The final total is truncated to a whole milliliter — the same integer conversion the ProbaBaby iOS app uses, so both give identical answers.
The trimester bonus is +300 ml for the first trimester (weeks 1–12), +400 ml for the second (weeks 13–26), and +500 ml for the third (weeks 27–40). One honest footnote: this tool's second trimester ends at week 26, while our pregnancy weight gain calculator splits trimesters at week 13–27 — each mirrors its own in-app engine exactly, so we kept both boundaries as they are.
The activity bonus is +0 ml if you are sedentary (mostly sitting, light movement), +500 ml for moderate activity (regular walking, light exercise), and +1,000 ml if you are active (daily exercise, active lifestyle).
Unit conversions use exact constants: 1 lb = 0.45359237 kg for the engine math, and 1 US fl oz = 29.5735 ml for the ounce display. Cups and glasses always round up — cups per day = ceil(target ml ÷ 250) and glasses per day = ceil(target oz ÷ 8) — because a partial cup still needs to be drunk.
Worked example: at 65 kg, second trimester, moderate activity, the baseline is 65 × 30 = 1,950 ml; adding the +400 ml trimester bonus and +500 ml activity bonus gives 2,850 ml — that is 12 cups of 250 ml, or about 96 oz (13 glasses of 8 oz). The maximum the calculator can produce is 6,000 ml (150 kg, third trimester, active).
Frequently asked questions
This calculator's guideline starts at 30 ml per kilogram of body weight, then adds 300–500 ml for your trimester and 0–1,000 ml for your activity level. At 65 kg in the second trimester with moderate activity, that works out to 2,850 ml a day — about 12 cups of 250 ml. This is a general guideline; consult your healthcare provider for personalized hydration advice.
Proper hydration supports amniotic fluid and nutrient delivery to your baby, and needs grow as pregnancy progresses. The calculator adds +300 ml in the first trimester (weeks 1–12), +400 ml in the second (weeks 13–26), and +500 ml in the third (weeks 27–40).
Yes. A sedentary routine (mostly sitting, light movement) adds nothing to the baseline, moderate activity (regular walking, light exercise) adds 500 ml, and an active lifestyle (daily exercise) adds 1,000 ml per day.
Yes — toggle the weight unit to lbs and the slider converts in place (88–330 lbs). The engine converts pounds to kilograms with the exact factor 1 lb = 0.45359237 kg, and the result is then shown in US fluid ounces (1 oz = 29.5735 ml) instead of milliliters.
A cup is 250 ml and a glass is 8 US fl oz. Both counts round up — cups = ceil(target ml ÷ 250), glasses = ceil(target oz ÷ 8) — so the goal is always fully covered.
No. This is a general guideline. Consult your healthcare provider for personalized hydration advice — especially if you have a condition that affects how much fluid you should drink.