Sprinkler Calculators
Work out precipitation rates, zone sizes and run times, check head spacing and coverage, and plan a first-pass system layout. Audit an existing system with a catch-can test, then program cycle and soak or seasonal adjustments. Each calculator answers one question, shows its formula, and works in US or metric units.
Which sprinkler calculator do you need?
Find your question below. Each calculator does one job, so picking the right one gets you a precise answer.
| Your question | Use this calculator | How it works |
|---|---|---|
| What precipitation rate will my sprinklers apply? | Sprinkler Precipitation Rate Calculator | Head GPM and spacing (square or triangular), or zone GPM ÷ area. |
| How many minutes should each zone run on my controller? | Sprinkler Run Time Calculator | Each zone's rate, type and target depth become minutes, cycles and program length. |
| How many heads can I put on one valve? | Sprinkler Zone Calculator | Available supply GPM, with a safety margin, ÷ each head's GPM. |
| How far apart should I space my sprinkler heads? | Sprinkler Head Spacing Calculator | Throw radius, pattern and wind give a recommended spacing. |
| How many square feet does one sprinkler head cover? | Sprinkler Coverage Calculator | Radius and arc give the covered area, plus a head-to-head check. |
| How many sprinkler heads do I need for my yard? | Sprinkler Head Count Calculator | Area dimensions, radius and pattern give an estimated head and row count. |
| What's the total GPM for a zone of sprinkler heads? | Sprinkler GPM Calculator | Nozzle GPM × head count, totaled and compared with supply. |
| What's the flow rate through a single nozzle? | Nozzle Flow Rate Calculator | Orifice diameter and pressure, or flow at a new pressure. |
| Are the heads in my zone matched, and what GPM do half or quarter heads need? | Matched Precipitation Calculator | Each head's flow and arc give its precipitation rate and a matched-zone check. |
| How do I measure what my sprinklers are actually putting down? | Catch Can Test Calculator | Can readings, test time and can size give a measured precipitation rate. |
| How evenly does my system water the zone? | Distribution Uniformity Calculator | Can readings give DUlq, CU and a run-time multiplier. |
| What's my system's scheduling coefficient? | Scheduling Coefficient Calculator | Grid readings give SC (average ÷ driest area) and a run-time multiplier. |
| How do I avoid runoff on clay soil or a slope? | Cycle and Soak Calculator | Sprinkler rate, soil intake rate and slope give max minutes per cycle and soak time. |
| How should I adjust run times through the seasons? | Seasonal Adjustment Calculator | Monthly ETo against the peak month gives a controller % and adjusted run times. |
| How long should I run a hose-end or oscillating sprinkler? | Hose End Sprinkler Output Calculator | Hose flow and pattern size, or a can test, give an application rate. |
| Where do I start planning a new sprinkler system? | Sprinkler System Design Calculator | Area, supply, pressure and head type give a first-pass head, zone and pipe estimate. |
| What size air compressor do I need to winterize my system? | Sprinkler Blowout CFM Calculator | Pipe size and zone flow give required CFM, max safe pressure and time per zone. |
All sprinkler calculators
Design and layout
- Sprinkler Head Spacing CalculatorRecommended head and row spacing from throw and wind
- Sprinkler Coverage CalculatorArea one head covers, plus a coverage check
- Sprinkler Head Count CalculatorEstimated heads and rows for your yard's area
- Sprinkler Zone CalculatorHeads per zone and zones needed from supply
- Sprinkler GPM CalculatorTotal zone GPM from nozzle flow and head count
- Nozzle Flow Rate CalculatorFlow from orifice size and pressure, or a new pressure
- Sprinkler System Design CalculatorFirst-pass heads, zones, GPM and pipe sizes
Precipitation rate and run times
- Sprinkler Precipitation Rate CalculatorRate from head GPM and spacing, or zone flow
- Sprinkler Run Time CalculatorMinutes per zone and total program length
- Matched Precipitation CalculatorPer-head precipitation rate and a matched-zone check
- Cycle and Soak CalculatorMax minutes per cycle to stop runoff
- Seasonal Adjustment CalculatorMonthly controller percentage from ETo relative to peak
Testing and audits
Sprinkler basics
What the standard formulas and audit guidelines say, in brief. Each calculator page goes into detail and cites its sources.
96.3 is the precipitation-rate constant
Rain Bird's irrigation design guidance derives the 96.3 constant in the precipitation-rate formula from converting one gallon over one square foot into an hourly rate, giving PR = 96.3 × GPM ÷ (head spacing × row spacing) for square-spaced heads.
Matched heads keep a zone even
Hunter Industries' technical notes on matched precipitation explain that a zone is matched when quarter-, half- and full-circle heads discharge at roughly a 1:2:4 ratio, so every part of the zone receives close to the same depth of water.
65% DU is EPA's bar for new systems
EPA WaterSense's New Homes irrigation audit guidelines require a newly installed system to reach a lower-quarter distribution uniformity (DULQ) of 65% or greater, measured with the catch-can method on the largest spray-irrigated area.
Cycle and soak stops runoff on clay and slopes
Texas A&M AgriLife Extension recommends splitting a zone's runtime into shorter cycles, with a break between cycles, whenever the sprinkler's precipitation rate is likely to exceed the soil's intake rate, which is most common on clay soils and slopes.
Local watering restrictions and any audit requirements from your water provider always come first. For the data behind these numbers, see the sprinkler precipitation rate chart and the soil infiltration rate chart.
Related calculator categories
- Lawn calculatorsWatering targets and schedules that set your run times
- Drip irrigation calculatorsEmitter spacing, zone flow and run times for drip
- Irrigation hydraulics calculatorsPipe sizing, friction loss and system GPM
- Scheduling and ET calculatorsEvapotranspiration, water requirements and budgets
- Cost and savings calculatorsIncluding what a sprinkler system costs to run
- All calculatorsEvery irrigation calculator by category
Sources and review
This page and its calculators are reviewed by Daniel Reeves, PE, CID. Last reviewed . See our methodology and editorial policy, or report an error.
- Rain Bird. Irrigation Design Tip: Calculating Precipitation Rates.
- Hunter Industries. Tech Irrigation Notes: Basics of Matched Precipitation. [VERIFY URL]
- EPA WaterSense. New Homes Irrigation Audit Guidelines.
- Swanson, C. & Fipps, G. Texas A&M AgriLife Extension. Preventing Runoff with Cycle and Soak Irrigation.