How would I calculate the sqft for a drip zone for the entire yard?
Maybe www.findlotsize.com will help you. Just enter your address, zoom in, and you can measure your sqft.
I could do that… I guess my question is… I am not drip watering the entire property… only the shrubs and trees. Do I only count those areas in the sqft or am I just making this way to difficult?
@Silent I’ve struggled with this for a while. Drip emitters are rated in GPH, but the PR is in in/hr. There’s a formula around here that is used to convert GPH to in/hr, but when it comes to the approximation is made to use a 1 sq.ft. are in the assumption. I don’t agree with that assumption for my particular scenario, but I’m sure it works for others.
What I did is look at my gallon per minute usage first. I have trees with three 2 GPH heads on each of them, and 4 trees.
Total trees GPH = 3 emitters/tree * 2 GPH/emitter * 4 trees = 24 GPH
Total trees GPM = 24 gal/hr * (1 min/60 gal) = 0.4 gal/min
From this link note that
water usage (gal) = AREA (sq.ft) * PR (in/hr) / 96.25
or
AREA (sq.ft) = water usage (gal/min) * 96.25 / PR (in/hr)
my PR is set to 0.4 in/hr
AREA (sq.ft) = 0.4 gal/min * 96.25 / (0.4 in/hr) = 96.25 (sq. ft)
This is what I did anyway. The nice thing is this only affects the water used calculation, so if I’m wrong I won’t kill any plants or flood my yard. 
This is really the only reason why I haven’t converted my tree drip zones to flex daily. I don’t know what to use as the Area to calculate the precipitation rate. I also don’t think 1 sq ft is appropriate for clay soil at least.
@JPedrego Here’s my solution that didn’t use the 1ft x 1ft assumption.
Basically, tweak the PR until you get the recommended run time from your local experts. Then if you care about the water usage reports back out the area calculation per this thread.
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If it were me I would use Google Earth to estimate my measurements, then go to www.netafim.Com and use their drip measurement calculations. They have formulas to calculate the linear feet you will need. I recommend using drip tubing with inline pressure compensating emitters. If you have clay soil you’ll want to to go with .4 or .6 gallon per hour emitters. Emitters are spaced 12 or 18 inched apartment. What are you growing? Turf? Shrubs?
The various formulas will enable you to calculate total flow. You will also need to know the spacing between rows. Toro also has excellent drip design guides too. I’m not a fan of point-source emitters. Hope this helps a little
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@robertokc. The problem I have with the online calculators is that they assume uniform spacing. That would work in my garden, but for my shrubs and trees there is no uniformity. My shrubs are anywhere from 2 to 15 feet apart, with single point emitters. The trees are easily 40-75 feet apart, with three emitters per tree. I never get how to translate that into the question of emitter spacing in the calculator. What am I missing?
Not sure about the calculations, but you can run blank 17mm Netafim, Toro or Rain Bird tubing between shrubs and trees. Then, using the tubing with built in emitters, build tree and shrub circles at the drip line of the shrubs and trees. Ask the guys down at Sprinkler World of Arizona for advice if that is where you shop.
You simply use 17mm tees, elbows, crosses, etc. You can bury the subsurface drip and include flush caps at the end of the runs to periodically flush the lines. I saw that spaghetti tubing with individual emitters at shrubs in Arizona and they were a pain in the butt. By running circular shrub and tree rings you also encourage root growth, adding protection against trees uprooting from windstorms in Arizona.
I see. I’ve lived here for 22 years. It seems all they ever install around here is the cheap and easy stuff. Go figure.
It’s the same thing here. Cheap and easy with horrible design. However not much of the spaghetti tubing is used here. We are mostly sprinkler irrigation here.