We’ve all heard the rule: 64 ounces of water per day is essential to healthy living. But is that really how much water you should be drinking? If so, how is Tom Brady still alive? (He’s admitted to drinking close to 300 ounces of water per day). When it comes to water intake, all humans are not created equal; the amount of water you need depends on multiple factors.

The more you exercise, the more you need to drink

People often feel like as long as they’re drinking water while they exercise, they don’t need to drink much before and after. Even though that glass of wine might be calling your name post-workout, if you sweat a lot, you need to drink a lot (of water). It’s important to replenish lost fluids after exercise to make sure your muscles recover properly. If you just completed a hard workout, opt for something like Smartwater or water mixed with a sports drink in order to replenish electrolytes.

Environmental factors play a role

When you exercise, you sweat. The same goes for hot temperatures. If you’re traveling through the Grand Canyon in July, you’re going to need more water than if you’re sitting on your couch watching television in December. It’s imperative that you replenish fluids in your body as you sweat them out in order to avoid dehydration. If it’s a summer day and you’re about to do a HIIT workout outside, you should be drinking between 16 and 32 ounces every hour.

When it comes to water intake, size matters

Your height and weight also play a role in how much water you need. A 170-pound, six-foot man will need more water than a 120-pound, five-foot woman. Plus, size can also affect how much you sweat while working out. To see how much water you need for your size and your workout intensity, try using a hydration calculator.

Your overall health condition is an important factor

The foods you eat and how much you work out both affect your overall health. If you eat high-sodium foods or have high blood pressure, you’ll need more water than someone who doesn’t. Also, hydration is even more important if you’re pregnant. If you have any health problems, you should discuss with your doctor the proper water amount for your body.

So, how much water do you actually need?

Clearly, the answer is complex. If you exercise intensely five days per week and live somewhere like Arizona, you’ll probably need about 100 ounces per day. But if you take a daily, 20-minute morning walk in 65-degree weather, you might need more like 64 ounces. The true amount depends on your individual needs. You can always talk to your doctor or a nutritionist or personal trainer to get a better idea of how much water is enough for you.

Quick tips to stay hydrated

• Keep a water bottle at your desk – if your water is in plain sight, you’re more likely to drink it
• Don’t chug a bottle of water 10 minutes before you work out – You probably won’t feel that great afterward, and you also won’t be hydrated. Make sure to drink morning through night to be in the best shape possible for the gym
• Set an alarm – If you tend to get caught up in your work and never remember to take a sip, set an alarm every hour throughout the work day to remind yourself to drink a glass of water.