Agriculture Calculators
Work out the flow, volume and run time your field needs: GPM per acre, acre-inches and acre-feet, center pivot output and well capacity, furrow and flood set times, and seasonal crop water use for row crops, orchards, vineyards and greenhouses. Each calculator shows its formula and works in US or metric units.
Which agriculture 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 |
|---|---|---|
| How much flow (GPM) do I need per acre for my field? | GPM per Acre Calculator | Peak ET, acres, efficiency and pumping hours give required GPM. |
| How do I convert acre-inches to gallons or cubic feet? | Acre-Inches Calculator | Converts acre-inches to gallons, ft³, m³, or from GPM × hours. |
| How many gallons or acre-inches are in an acre-foot? | Acre-Feet Calculator | Converts acre-feet to gallons, acre-inches, m³, or area × depth. |
| How much depth will a given flow and run time apply? | Irrigation Application Depth Calculator | Depth = GPM × hours ÷ (453 × acres), gross and net of efficiency. |
| How long should I run a set to hit a target depth? | Irrigation Set Time Calculator | Hours = 453 × acres × depth ÷ GPM, plus sets per day. |
| How much water will my crop need for the whole season? | Crop Water Requirement Calculator | FAO-56 Kc stage curve and monthly ETo give a season total. |
| What's my crop's coefficient (Kc) today? | Crop Coefficient Calculator | Interpolates the FAO-56 stage curve for the date, climate-adjusted. |
| How much depth does my center pivot apply, and at what rate? | Center Pivot Calculator | GPM, acres and timer % or rotation time give in/day. |
| How many acres does my center pivot actually cover? | Center Pivot Acreage Calculator | System length, end gun, partial arc and corner arm. |
| How much depth does furrow irrigation put on my field? | Furrow Irrigation Calculator | Furrow spacing, length, inflow per furrow and set time. |
| How long should I flood my field for a target depth? | Flood Irrigation Calculator | Inflow (GPM or cfs) and basin or border area give time or depth. |
| What travel speed should my traveling gun run at? | Traveler Irrigation Calculator | Travel speed, lane spacing and GPM give application depth. |
| Can my well keep up with my acreage at peak demand? | Irrigation Well Capacity Calculator | Well yield vs. required flow, and the maximum acres supported. |
| How much water does each tree in my orchard need daily? | Orchard Irrigation Calculator | ETo × Kc × canopy cover × spacing gives gallons per tree. |
| How much water does each vine in my vineyard need daily? | Vineyard Irrigation Calculator | ETo × canopy-based Kc × vine spacing, with an RDI % option. |
| How much water does my greenhouse crop need each day? | Greenhouse Irrigation Calculator | Container size, an ET estimate and leaching fraction give daily water. |
All agriculture calculators
Flow, volume and application math
- GPM per Acre CalculatorRequired pumping flow per acre from peak ET and efficiency
- Acre-Inches CalculatorConvert acre-inches to gallons, cubic feet and cubic meters
- Acre-Feet CalculatorConvert acre-feet to gallons, acre-inches and cubic meters
- Irrigation Application Depth CalculatorDepth applied from GPM, run time and acreage
- Irrigation Set Time CalculatorRun time needed to apply a target depth
Crop water need
Field and well systems
- Center Pivot CalculatorDepth per revolution and in/day from GPM and acres
- Center Pivot Acreage CalculatorIrrigated acres from system length, end gun and arc
- Furrow Irrigation CalculatorDepth applied from furrow spacing, inflow and set time
- Flood Irrigation CalculatorTime or depth for basin and border flooding
- Traveler Irrigation CalculatorApplication depth from travel speed and lane spacing
- Irrigation Well Capacity CalculatorWell yield vs. required flow and maximum acres served
Agriculture irrigation basics
What extension research and FAO guidance say, in brief. Each calculator page goes into detail and cites its sources.
An acre-inch is 27,154 gallons
Kansas State Research and Extension puts an acre-foot at 325,851 gallons, or 12 acre-inches, and an acre-inch delivered over an hour at close to 453 gallons per minute — the constant behind the application-depth and set-time formulas.
Crop coefficients change through the season
FAO Irrigation and Drainage Paper 56 splits a crop's growing season into four stages — initial, development, mid-season and late season — each with its own crop coefficient (Kc), rather than one number for the whole season.
Application efficiency depends heavily on the system
USDA's Agricultural Research Service reports buried drip irrigation can exceed 95% application efficiency, center pivots typically run 75 to 85%, and surface methods such as furrow or flood irrigation typically run 30 to 50%.
Deficit irrigation is a set fraction of full ETc
UC Cooperative Extension in Sonoma County notes common regulated deficit irrigation (RDI) coefficients for winegrapes range from 0.35 to 0.65 of full crop evapotranspiration, adjusted for soil depth and variety.
Well permits, water rights and allocation limits vary by state and irrigation district — check with your local water authority before relying on these figures for compliance. For more data, see the crop coefficient table and the full reference section.
Related calculator categories
- Scheduling and ET calculatorsEvapotranspiration, water requirements and budgets
- Irrigation hydraulics calculatorsPipe sizing, friction loss and system GPM
- Soil calculatorsWater holding capacity, infiltration and water quality
- Fertigation calculatorsInjection rates, ratios and nutrient concentrations
- Cost and savings calculatorsWater, energy and system cost estimates
- 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.
- Rogers, D. H., and M. Alam. Irrigation Formulas and Conversions. Kansas State Research and Extension.
- Allen, R. G., L. S. Pereira, D. Raes, and M. Smith (1998). Crop Evapotranspiration — Guidelines for Computing Crop Water Requirements. FAO Irrigation and Drainage Paper 56.
- USDA Agricultural Research Service. Irrigation.
- University of California Cooperative Extension, Sonoma County. Regulated Deficit Irrigation Coefficients.