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Use These Garden Water Calculators for Smarter Watering
Accepts Either US or Metric Measurements

Watering Lettuce Plants With A Watering Can After Using A Garden Water Calculator.

Did you ever wonder how many gallons or liters of water you need to add to your garden every day? And what about watering potted plants? Well, wonder no more. Our handy herb or vegetable garden water calculators will solve that problem.

Get rid of the guesswork. Once you know how to calculate the amount of water for the garden, it’s easy to keep your plants well-hydrated. By the way, these calculators work for lawns and landscaping too!

For convenience, the first calculator is for square or rectangular gardens.

This will also work for square or rectangular pots. You’ll have to convert the needed water results to ounces or deciliters for smaller pots. Otherwise the numbers won’t look reasonable.

Right below the garden calculator we have a water calculator for plants in round pots. With these calculators, you can figure out the water needs for any round, square, or rectangular garden or pot.

Don’t forget to check our article about all the remarkable ways that plants use water.

Garden Water Calculator for Square or Rectangular Gardens

Depending on the sizes of the plants and the climate, your garden may need more than one inch of water per week. Always check the soil moisture to make sure.

The calculator can handle these situations. Suppose you want to water your plants twice a week. That would be 1 inch X twice a week = 2 inches of water.

Three times a week would be 3 inches of water. The calculator will still give the weekly and daily requirements.


Use This Water Calculator for Potted Plants

Since any pot is much smaller than a garden or raised bed, using gallons or liters wouldn’t make sense for smaller pots. Because of that, we switched the water requirements to fluid ounces and deciliters. That gives reasonable numbers that make sense.

If your potted plants are outside, the soil tends to dry out faster than inside plants. Adjust the additional water needed for outside plants based on any rain they already received.

How the Garden Water Calculators Work

On average, gardens need about two inches of water every week during the hot summer months.  During moister conditions, the garden needs one inch or less every week. It all depends on how much rain fell in the past few days.

Let’s say we have a raised bed garden that’s 10 feet long X 4 feet wide.  That garden has an area of 10 ft X 4 ft = 40 square feet.  Here’s the formula for figuring the water usage:

Garden area in square feet X inches of water X 0.623 = gallons of water needed.

For the metric system, we’ll use this formula:

Garden area in square meters X centimeters of water X 10 = liters of water needed.

The numbers 0.623 and 10 are constants. Our article The Best Rainwater Harvesting Calculator explains these numbers.

We checked the rain gauge and saw that we got 1/2-inch of water so far this week. That means the 40 square-foot raised bed garden needs another 1/2-inch of water. Here’s how to convert inches of water into gallons:

40 square feet X 1/2-inch more water X 0.623 = 12.5 gallons of water needed for the rest of the week (rounded from 12.46).  If there are 4 days left in the week. 12.5/4 = 3 gallons per day.

A handy rule-of-thumb is to remember that the number of gallons needed for 100 square feet with 1 inch of water equals 62.3 gallons.

Soaker or drip irrigation is better than watering cans, since it’s 85% – 90% efficient. After setting it up, it’s a hassle-free way to water the garden.

The greatest benefits come from no-till gardening methods. They allow the soil to hold moisture much longer. Since uncovered soil loses water at a higher rate, even a layer of straw mulch will keep the soil moister.

With the help of these calculators, you now know how to calculate the daily and weekly water usage for the garden or potted plants. We hope you find them useful.


Rain Gauges

To make your water calculations more accurate, it helps to have a rain gauge. That way, you can adjust for the water your plants already received.

These are rain gauges that have high reviews on Amazon.

Bob Styer

As a child, I hated gardening. That was mainly because Dad expected us to work in the garden every so often even though we thought play was more important. Over the years, though, I've developed a real appreciation for growing things. Whether you're growing plants for food or to enjoy their beauty, gardening can make your life better. Seize the moment!

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