How Much Water Does A Garden Need?


So, Tell Me – How Much Water Does A Garden Need?

Your garden needs an inch of water per week.  But, then you say, “But, that doesn’t exactly answer the question – how much water does a garden need?  How do I know just what is an inch per week really is?”

An inch of garden water per week.

Well, the industry standard average amount of water the plants in your backyard garden need each week is about one inch…give or take a bit.

If the garden doesn’t get enough water, the plants will feel drought conditions and start to wither and die.

If the veggie plot gets too much water, the plants may become infected with a variety of diseases or they will drown because the roots can’t breathe.  Then, the plants will eventually die.


Okay…Hmmm…So, How Do We Know For Sure What an Inch of Water Is?

Measure an inch of water.

Since watering is such an integral part of the veggie growing process, there are several solutions to this dilemma.

  • Buy some water monitoring sensors.
  • Educate yourself on some accurate ways to gauge the amount of water your plants receive.



The Following Information Contains Easy-to-Follow Technical Items!

If you are still reading this article, then…congratulations…you are now going to learn how to properly assure that you can meet the one-inch-per-week water criteria for your garden!

There will be a calculation or two…but, just take it one small step at a time.  It’s not as hard as it looks.

Topics to be covered:

  • How to estimate the water needs of your garden…by plant…by row…or, by the entire garden.
  • How to calculate the amount of water delivered to your garden using each of the 3 basic water delivery methods; rain, garden hose, and soaker hose.


So, Really…How Many Gallons of Water Do We Need?

How many gallons of water for garden?

The short answer is to measure the length and the width of the area…in feet…that you want to water.  Multiply the two numbers to get the square footage and determine the amount of water you need from this table.

Example:  If your total area to be watered is 350 square feet, then you will need the total amount of water shown on the right for 50, 100, and 200 square feet.  Add 31.17 + 62.34 + 124.68 to get roughly 218 gallons of water needed each week to meet the one inch requirement for a 350 square foot area.

One square foot is about the area taken up by one plant.  Thus, it will need a little over a half gallon (0.62 gal) per week.

NOTE:  It is best to spread the water out so that the plants get several waterings per week…for instance…half of the water on Monday…and, the other half on Friday.

Dare to see the detailed calculations used to create this table.


Raindrops Keep Fallin’ on My Garden Bed

 Raining in the garden.

A moderate rain can deliver about ½ inch of water in a couple of hours.  A heavy rain may drop an inch in a little over 3 hours.

Rainfall table.


Some Garden Hose for My Lady and Gentlemen Plants…

The amount of water a garden hose can apply to your backyard veggies…measured in gallons per minute (gpm)…is dependent upon three basic factors; The diameter of the hose, the length of the hose, and the water pressure in pounds per square inch (psi),

Garden hose 1/2 inch diameter gpm.


Garden hose 5/8 inch diameter gpm.


Garden hose 3/4 inch diameter gpm.

Example:  A garden hose 5/8 inches in diameter and 25 foot long will produce 50 gallons of water per minute at 50 psi.  So, based on the water table above…a 1,000 square foot garden will need about 623 gallons of water to meet the one inch rule…meaning this garden hose will be spraying water between 12 and 13 minutes.

One other way to determine the gallons per minute from a garden hose is to turn it on and fill a 5, 10, or 20 gallon container…or even a 55 gallon rainwater barrel if you are using them like I am.  How much time does it take to fill the container?  If it takes 11 minutes to fill a 55 gallon rain barrel, then your hose is pumping out 5 gallons of water per minute.

Take a look at my product reviews on select garden hoses.


Last…But Certainly Not Least…Soaker Hoses!

Soaker hose.


Soaker hoses are the perfect method to water your veggies.  They offer a slow release of water…giving the plant roots time to absorb it.  And, if the hoses are covered with mulch, almost no water will be lost due to evaporation.

The kicker is that the best water source for soaker hoses is the trusty rainwater barrel because of the low psi.



Water pressure regulator.


If you connect soaker hoses to a faucet, it is advisable to use a pressure regulator.  Otherwise the hoses can be damaged if the pressure is too high…or, at least, the end caps on the soaker hoses may pop off.

So, try to keep the pressure to around a trickle…about 10 psi (25 psi at the most).

With that in mind, 100 foot of soaker hose at 10 psi will give your garden about 54 gallons of water per hour…a little less than a gallon a minute.  If you are brave enough to try 25 psi, on the same length of hose, you can get up to about 225 gallons of water per hour…a bit over 3.5 gallons a minute.


My Neighbor Jed

Old Jed has been my neighbor for quite some time now.  He’s retired…but, for most of his career years he was a farmer.  And, he loves a good story…

Jed's pond frog.

He had a pond nestled in a little valley on his farm and one day, as he was walking along the edge of the water, he spotted a frog.

He picked it up and as he started to put it in his pocket the frog said, “Kiss me and I will become a beautiful wife for you!”

Jed ignored the frog and continued to put it in his pocket.

“Didn’t you hear what I said?”  The frog snapped at him.

Jed looked at the frog and said, “You know…at my age…I think I’d rather just have a talking frog.”


Read more about Jed’s Adventures and Misadventures at the bottom of other pages at The Perfect Vegetable Garden.


How do you water your garden?  And, what “measures” do you take to ensure your veggies are getting an inch of water per week?  Add some comments or send an email:


Jim, the Lifelong Gardener




















The Detailed Calculations

Let’s start small by looking at the water needs of an area 12 inches long, 12 inches wide…with the understanding that the water is to be 1 inch deep:

Step #1

Cubic inches equal the length times the width times the depth…or CI = L x W x D.

NOTE:  The depth (D) will always be one inch which is the depth of the water you want to apply to the area.

So, for an area 12 inches long and 12 inches wide, the computation would be 12 x 12 x 1 = 144 cubic inches.

Step #2

Multiply the total number of cubic inches (144) times the gallon factor (0.0043290043) to get the total number of gallons needed to supply one inch of water to an area that is 12 inches long and 12 inches wide (or, one square foot).

144 x 0.0043290043 = 0.623376619 gallons of water


How Much Water to Give One Plant?

 Sprinkler watering the garden.

Hence, each square foot of garden, which is about the space taken up by the average veggie plant, needs a little over a half gallon (0.623376619 gallons) of water per week to get their weekly inch of water.

This is especially beneficial to all container gardening enthusiasts.  Now, they know that just a bit over a half gallon of water per week should be adequate for each of their container plants.

That was easy.  Time to expand on it!


Shall We Continue?

Looking at water needed for a row of veggies…

Now that we know how to determine water needs for one square foot of garden space, it is time to look at the total water needs of one entire row in the garden.  Remember that all measurements in feet have to be converted into inches…12 inches per foot…means that a 20 foot long row will actually be 20 x 12 = 240 inch long row.

Staying within the row will allow us to keep the width at 12 inches.  Then, we have 240 inches times 12 inches times 1 inch equals 2,880 cubic inches.

Multiplying 2,880 cubic inches times the gallon factor (0.0043290043) equals 12.5 gallons of water.

To summarize, a 20 foot long row of veggies will need about 12.5 gallons of water per week to get their one inch minimum requirement.  Again…as in the case of the one-plant container…spread the water out over several applications during the week.


Now, for the final calculation…

How much is needed for the entire backyard garden?

It should be easy by now…right?

Let’s say that the garden is 30 feet long and 20 feet wide.  Then the garden is actually 360 inches long and 240 inches wide…which, when multiplied together…times the 1 inch depth…equals 86,400 cubic inches.

Multiply 86,400 cubic inches times the gallon factor (0.0043290043) equals about 374 gallons of water needed per week to meet the one inch necessity.

Now, that wasn’t so hard, was it???



2 thoughts on “How Much Water Does A Garden Need?

  1. Kimi Reply

    There are definitely some interesting calculations on watering. What type of climate would these calculations be for? I am in a semi arid climate and I know half an inch to an inch is good for one watering on those dry hot summer months, and we would water at least 3 times a week.

    Have you ever heard of the tuna can test? Put out a tuna can (since it collects about an inch of water) to measure how much water certain areas of your lawn are getting watered.

    • Jim Reply

      Hi Kimi,

      The calculations used to determine the amount of water needed for your garden plants…based on the one inch per week standard…are universal.  However, the hotter and drier climates around the world have an additional consideration…rapid evaporation.  Thus, you may have to adapt to your area by making minor adjustments to your irrigation needs.  You may possibly need an extra half inch of water per week.

      Every gardener should use some type of rain gauge.  Popular techniques include using tuna cans, cat food cans, or even #10 cans such as those containing coffee or other food items.  As long as the containers have straight sides from top to bottom, they will make excellent rain gauges.

      Several cans placed around the garden in random areas can give you a good idea if there are any variations in water distribution.  Even rainfall can deposit water across the garden area unevenly.  I have had unique occasions where a section of my garden remained dry after a moderate rain.

      Thanks, for stopping by.


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