We’re mostly made of water, and our bodies use it like crazy to perform almost every function. We also lose a lot of it during natural waste processes—sweating, breathing, and using the bathroom. As an old guideline, health professionals and clinics have recommended drinking anywhere from 12 to 15 cups of water a day, or more familiarly, a baseline of eight glasses.

Some brands who package their beverages in plastic bottles have taken to reframing this recommendation, which comes from the Mayo Clinic, in terms of bottles, as in: How many bottles of water should I drink in a day? And because our mission is to eliminate single-use plastics, and because single-use plastic bottles are one of the world’s largest offenders in plastic pollution, obviously we are not in favor of this mindset. Instead of thinking in terms of “how many bottles,” we’d urge you to think in terms of the amount of water to drink, whether that’s in cups, ounces, or liters (that’s right–you should be drinking several liters a day!).

Now that we’ve moved on from thinking about our water intake in terms of bottles of water, let’s revisit what the experts say. To begin with, we can consume water from many sources, not just by drinking it, though that obviously is the easiest way to stay hydrated. We get water from the food we eat and other beverages, too. But a few factors determine how much water you should drink on a daily basis.

First, your metabolism matters. How fast your body processes what you give it determines how quickly it will use water to aid its many processes, like digestion, perspiration, and movement, to name just a few. Generally speaking, the more active you are, the more water you need, because your muscles and cardiovascular system require it. Water regulates our temperature, lubricates and cushions our joints, and protects our sensitive tissues–all processes that can be affected by exercise or intense physical activity. Simply put, the more you move, the more you need to drink. Aim to drink anywhere from 64 ounces to 128 ounces of water a day if you are active, while 32 ounces to 64 ounces is a safe bet if you have a less active lifestyle.

Secondly, your environment is a factor. Naturally, if you live in a warmer climate, you will require more water–hotter weather makes us perspire more to keep us cool, and this requires hydration. Our bodies are constantly trying to regulate our temperatures–we shiver when we are cold, and we sweat when we’re too hot. Every process takes water, but being too warm is especially water-expensive.

Last, your overall health is a huge factor, too. Healthy people should try to stick to the 64 ounces guideline, but those with health problems or at-risk people–including pregnant women–likely will need to consume significantly more to account for their bodies being under more duress.

Since we’re not thinking in terms of “number of water bottles” to meet our daily H2O requirements, we can instead shift to using one single, high-quality bottle that has a high volume capacity and that is easily refillable. Obviously, if you’re drinking frequently from a single container, you want it to be clean and durable, which leads us to decide between which kind of bottle is the best water bottle.

You may have an old favorite plastic bottle you’ve been reusing, trying to save it from the trash heap, and that’s commendable. But it’s still far from ideal! No matter how long you use a plastic water bottle, it will eventually break down beyond the point of usability and will need to be discarded. Even the sturdiest of plastic bottles will break, warp, or diminish in quality in some way over time. That cycle of disposal is what makes single-use plastics so dangerous: they wreak havoc on the environment.

There are clear environmental advantages to using a recycled steel water bottle, specifically one made from 90-percent post-consumer recycled steel. When you see certified 90-percent post-consumer recycled steel in use, you can feel confident in its quality but also know that it was made with a responsibility to the environment in mind. But saving the planet–a worthy cause, of course!—is not the only reason to get your daily water supply from a stainless steel bottle.

Stainless steel water bottles will beat out plastic bottles in both the long run and the short term because of their superior durability and cleanliness. Plastic is porous and soft, which is why it retains odors and tastes, and the tiny scrapes and scratches it naturally picks up create breeding grounds for bacteria that simply cannot thrive in the more sterile environment that 18/8 stainless steel provides. When you drink water from a stainless steel water bottle, it’s cleaner, stays colder longer, and is much more beneficial for the environment. And, unlike most standard plastic bottles, it’s easier to fit larger quantities to help you meet your daily requirements—Klean Kanteen makes options all the way up to 64 ounces.

Humans use an unfathomable 1.2 million plastic bottles per minute, a clearly unsustainable number for the health of our planet. Getting your daily water requirements should not add to that figure! Instead, get your 64 to 128 ounces of water a day from a clean, durable, high-quality recycled stainless steel water bottle.