Water
How many gallons is an inch of water a week?
About 0.62 gallons per square foot, so a 4x8 bed needs roughly 20 gallons to get its inch.
How this works
The old rule — an inch of water a week — turned into gallons for your bed. Water deep and seldom rather than a daily sprinkle, and skip the week it rains an inch on its own.
Questions people ask
How do I know if I have delivered an inch?
Put a straight-sided tin under the sprinkler and time how long it takes to fill an inch. That number is your watering time for the rest of the season.
Is an inch a week right for everything?
It is a starting point for most vegetables in loam. Sandy soil wants the same total split into more frequent smaller waterings; clay wants fewer and deeper.
Does rain count towards the inch?
Yes, that is the point of measuring in inches. A rain gauge and this figure between them tell you whether you owe the garden anything.