Per kilogram
Water Intake for 55 kg
Quick answer
A 55 kg (121 lb) adult should drink about 2.1 litres (72 fl oz, or 8.5 glasses) of water a day at a moderate activity level in a temperate climate. Needs range from roughly 1.7 litres on a quiet, cool day to about 2.7 litres when active or in heat — add more for exercise, pregnancy, and illness.
Fine-tune
Your daily goal: 2.1 litres, 8.5 glasses.
Your daily goal
of water a day · about 8.5 glasses or 4 half-litre bottles
- 2.1
- Litres
- 72
- Ounces
- 8.5
- Glasses
Your sip schedule
- 7:00 AM · Start the day1.5 glasses
- 9:48 AM · Top up1.5 glasses
- 12:36 PM · Top up1.5 glasses
- 3:24 PM · Top up1.5 glasses
- 6:12 PM · Top up1.5 glasses
- 9:00 PM · Wind down1.5 glasses
Ease off after 9:00 PM for better sleep.
Electrolytes? Skip them today
For everyday hydration, plain water and a normal diet cover your electrolytes just fine.
A friendly estimate for healthy adults, not medical advice. Your needs rise with heat, exercise, illness, pregnancy, and some medications. Don't drink more than ~1 litre per hour.
How much water is that? A 55 kg breakdown
For a 55 kg (121 lb) adult, the daily drinking goal lands near 2.1 litres (72 fl oz) at a moderate activity level. That's about 8.5 glasses or 4 half-litre bottles. On a quiet, cool day you might need as little as 1.7 litres; on an active day in the heat, closer to 2.7 litres.
| Body weight | Litres | Ounces | Glasses |
|---|---|---|---|
| 55 kg | 2.1 | 72 | 8.5 |
| 50 kg | 2 | 66 | 8 |
| 60 kg | 2.3 | 77 | 9 |
| 45 kg | 1.8 | 60 | 7 |
| 65 kg | 2.4 | 83 | 10 |
Where the 55 kg number comes from
The baseline is roughly 30–40 ml of water per kilogram of body weight, the widely cited rule of thumb backed by the U.S. National Academies and EFSA. A 55 kg person therefore lands near 2.1 litres before we layer on activity and climate.
The number above assumes a moderately active day in a temperate climate. Add about 350 ml (12 oz) for every half-hour of exercise, and around 10% more in hot or humid weather. Pregnancy, breastfeeding, fever, and some medications push it higher still. The calculator above adjusts all of this live — try it.
Don't drink it all at once
Your kidneys can clear only about 1 litre of water per hour. Spreading the goal across the day — and easing off in the last two hours before bed — keeps you comfortable and avoids nighttime bathroom trips. Pale yellow urine is a good everyday check that you're in the right zone.
Make it exact for 55 kg
Add your real activity, climate, and life stage to dial in a goal made for you — not just your weight.
Frequently asked
How much water should a 55 kg person drink a day?
A 55 kg (121 lb) adult should drink about 2.1 litres (72 fl oz) of water a day at a moderate activity level — roughly 8.5 glasses or 4 half-litre bottles. Needs range from around 1.7 litres on a quiet day to about 2.7 litres when you're active or in heat.
How many glasses is that for 55 kg?
For a 55 kg adult, 2.1 litres is about 8.5 standard 250 ml glasses (72 fl oz, or 4 half-litre bottles).
Is 30 ml per kg right for 55 kg?
30 ml per kg gives 1.7 litres, a sensible baseline for a 55 kg adult at rest. Most people do better a little higher, near 2.1 litres, especially once activity and climate are factored in.