Irrigation Zone Run Time Calculator
ANA›Life Services Authority›National Calculator Authority›Irrigation Zone Run Time Calculator
.calc-container { max-width: 640px; margin: 2rem 0; padding: 1.5rem; background: #fff; border: 1px solid #ddd; border-radius: 8px; box-shadow: 0 1px 3px rgba(0,0,0,0.06); font-family: system-ui, -apple-system, sans-serif; } .calc-container h3 { font-family: Georgia, serif; font-size: 1.15rem; color: #1a1a1a; margin-bottom: 1rem; padding-bottom: 0.5rem; border-bottom: 2px solid var(--ac, #3d5a80); } .calc-row { display: flex; align-items: center; gap: 0.75rem; margin-bottom: 0.75rem; flex-wrap: wrap; } .calc-row label { min-width: 160px; font-size: 0.9rem; color: #333; font-weight: 500; } .calc-row input[type="number"], .calc-row select { flex: 1; min-width: 120px; max-width: 200px; padding: 0.5rem 0.6rem; border: 1px solid #ccc; border-radius: 4px; font-size: 0.9rem; font-family: system-ui, sans-serif; color: #1a1a1a; background: #fafaf8; } .calc-row input:focus, .calc-row select:focus { outline: none; border-color: var(--ac, #3d5a80); box-shadow: 0 0 0 2px rgba(26,74,138,0.12); } .calc-row .unit { font-size: 0.82rem; color: #888; min-width: 30px; } .calc-btn { display: inline-block; margin-top: 0.5rem; padding: 0.55rem 1.5rem; background: var(--ac, #3d5a80); color: #fff; border: none; border-radius: 4px; font-size: 0.9rem; font-weight: 600; cursor: pointer; font-family: system-ui, sans-serif; } .calc-btn:hover { opacity: 0.9; } .calc-result { margin-top: 1.25rem; padding: 1rem 1.25rem; background: #f0f6fc; border-left: 3px solid var(--ac, #3d5a80); border-radius: 0 6px 6px 0; display: none; } .calc-result.visible { display: block; } .calc-result-label { font-size: 0.78rem; text-transform: uppercase; letter-spacing: 0.06em; color: #666; margin-bottom: 0.25rem; } .calc-result-value { font-size: 1.6rem; font-weight: 700; color: var(--ac, #3d5a80); } .calc-result-detail { font-size: 0.85rem; color: #555; margin-top: 0.5rem; line-height: 1.5; } .calc-note { margin-top: 1rem; font-size: 0.8rem; color: #888; font-style: italic; } .calc-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 0.75rem; margin-top: 0.75rem; } .calc-grid-item { padding: 0.6rem 0.8rem; background: #f8f9fa; border-radius: 4px; border: 1px solid #eee; } .calc-grid-item .label { font-size: 0.75rem; color: #888; text-transform: uppercase; letter-spacing: 0.04em; } .calc-grid-item .value { font-size: 1.1rem; font-weight: 600; color: #1a1a1a; } @media (max-width: 720px) { .calc-row { flex-direction: column; align-items: flex-start; gap: 0.3rem; } .calc-row label { min-width: auto; } .calc-row input[type="number"], .calc-row select { max-width: 100%; width: 100%; } .calc-grid { grid-template-columns: 1fr; } } .calc-chart { margin: 1rem 0; text-align: center; } .calc-chart svg { max-width: 100%; height: auto; } .calc-chart-legend { display: flex; flex-wrap: wrap; justify-content: center; gap: 0.6rem 1.2rem; margin-top: 0.6rem; font-size: 0.8rem; color: #555; } .calc-chart-legend span { display: inline-flex; align-items: center; gap: 0.3rem; } .calc-chart-legend i { display: inline-block; width: 10px; height: 10px; border-radius: 2px; font-style: normal; } .calc-related { max-width: 640px; margin: 2rem 0 1rem; padding: 1.25rem 1.5rem; background: #f8f9fa; border: 1px solid #e8e8e8; border-radius: 8px; } .calc-related h3 { font-family: Georgia, serif; font-size: 1rem; color: #1a1a1a; margin: 0 0 0.75rem; padding-bottom: 0.4rem; border-bottom: 2px solid var(--ac, #3d5a80); } .calc-related-list { list-style: none; padding: 0; margin: 0 0 0.75rem; display: grid; grid-template-columns: 1fr 1fr; gap: 0.4rem 1.5rem; } .calc-related-list li a { font-size: 0.88rem; color: var(--ac, #3d5a80); text-decoration: none; } .calc-related-list li a:hover { text-decoration: underline; } .calc-browse-all { margin: 0.5rem 0 0; font-size: 0.9rem; font-weight: 600; } .calc-browse-all a { color: var(--ac, #3d5a80); text-decoration: none; } .calc-browse-all a:hover { text-decoration: underline; } @media (max-width: 720px) { .calc-related-list { grid-template-columns: 1fr; } }
Irrigation Zone Run Time Calculator
Calculate the required run time for each irrigation zone based on your plants' water needs, your system's precipitation rate, and local evapotranspiration conditions.
Reference Evapotranspiration (ET₀) inches/week
Typical range: 0.5–3.0 in/week. Check your local extension service or weather station.
Crop / Plant Coefficient (Kc) dimensionless
Lawn ≈ 0.8, shrubs ≈ 0.5, vegetables ≈ 1.0, trees ≈ 0.5–0.9.
Sprinkler Precipitation Rate (PR) inches/hour
Rotary heads ≈ 0.4–1.0 in/hr; fixed spray heads ≈ 1.0–2.0 in/hr. Check head spec sheet.
Distribution Uniformity (DU) %
Well-designed systems: 75–85 %. Older or mismatched systems: 50–70 %.
Irrigation Days per Week days
How many days per week this zone will run.
Effective Rainfall This Week inches/week
Enter measurable rainfall that actually soaks in (not runoff). Leave 0 if none.
Calculate Run Time Fill in the fields above and click Calculate.
function irrCalc() { // --- grab inputs --- var ET0 = parseFloat(document.getElementById('irr-et').value); var Kc = parseFloat(document.getElementById('irr-kc').value); var PR = parseFloat(document.getElementById('irr-pr').value); var DU = parseFloat(document.getElementById('irr-dU').value); var days = parseFloat(document.getElementById('irr-days').value); var rain = parseFloat(document.getElementById('irr-rain').value);
// --- validation --- var errors = []; if (isNaN(ET0) || ET0 100) errors.push("Distribution Uniformity must be 1–100 %."); if (isNaN(days) || days 7 || days !== Math.floor(days)) errors.push("Irrigation days must be a whole number 1–7."); if (isNaN(rain) || rain 0) { resultDiv.innerHTML = 'Please fix the following:' + errors.map(function(e){ return ''; }).join('') + ''; return; }
// --- core formulas --- // Step 1: Adjusted ET (crop water need per week) // ETc (in/week) = ET0 × Kc var ETc = ET0 * Kc;
// Step 2: Net irrigation requirement (subtract effective rainfall) // NetIR (in/week) = max(ETc - rain, 0) var NetIR = Math.max(ETc - rain, 0);
// Step 3: Gross irrigation requirement (account for distribution uniformity) // GrossIR (in/week) = NetIR / (DU / 100) var DU_frac = DU / 100; var GrossIR = NetIR / DU_frac;
// Step 4: Total run time per week // TotalTime (hr/week) = GrossIR / PR var TotalTimeHr = GrossIR / PR; var TotalTimeMin = TotalTimeHr * 60;
// Step 5: Run time per session // TimePerSession (min) = TotalTimeMin / days var TimePerSession = TotalTimeMin / days; var TimePerSessionHr = Math.floor(TimePerSession / 60); var TimePerSessionRemMin = Math.round(TimePerSession % 60);
// Step 6: Weekly water applied (verification) // WaterApplied (in/week) = (TimePerSession/60) × PR × days × DU_frac var WaterApplied = (TimePerSession / 60) * PR * days * DU_frac;
// --- format helpers --- function fmt(n, d) { return parseFloat(n.toFixed(d)); }
var noIrrigation = NetIR ' + 'Crop Water Need (ETc)' + fmt(ETc,2) + ' in/week' + 'Net Irrigation Required' + fmt(NetIR,2) + ' in/week' + 'Gross Irrigation Required' + fmt(GrossIR,2) + ' in/week' + 'Total Run Time per Week' + fmt(TotalTimeMin,1) + ' min/week' + 'Run Time per Session (' + days + ' days/week)' + '' + (TimePerSessionHr > 0 ? TimePerSessionHr + ' hr ' : '') + TimePerSessionRemMin + ' min per session' + 'Effective Water Applied' + fmt(WaterApplied,2) + ' in/week' + '';
// advisory html += ''; if (TimePerSession 60) { html += '⚠️ Run time exceeds 60 min per session. Consider splitting into two cycles (cycle-and-soak) to reduce runoff.'; } else { html += '✅ Run time is within a practical range.'; } html += '
'; }
resultDiv.innerHTML = html; }
#### Formulas Used
1. Crop Evapotranspiration (ETc) ETc = ET₀ × Kc ET₀ = reference evapotranspiration (in/week); Kc = plant/crop coefficient.
2. Net Irrigation Requirement (NetIR) NetIR = max(ETc − Effective Rainfall, 0) [in/week]
3. Gross Irrigation Requirement (GrossIR) GrossIR = NetIR ÷ (DU / 100) [in/week] Accounts for non-uniform water distribution across the zone.
4. Total Weekly Run Time Total Time = GrossIR ÷ PR [hours/week]
5. Run Time per Session Time per Session = (Total Time × 60) ÷ Irrigation Days [minutes/session]
#### Assumptions & References
- Reference: Irrigation Association, Landscape Irrigation Scheduling and Water Management (2005).
More Calculators
- Sprinkler Head Coverage & Spacing Calculator
- Homework Completion Time Estimator
- Tutoring Session Rate Calculator
- Hardwood vs Laminate Cost Comparison Calculator
- Sprinkler System Water Pressure Calculator
- Double Glazing Condensation Risk Calculator
- SEER to EER Conversion Calculator — Efficiency Rating Comparison
- Furnace Efficiency Calculator — AFUE to Annual Fuel Cost
- HVAC Filter MERV Rating Selector and Airflow Restriction Estimator
- Static Pressure Drop Calculator for Duct Systems
- HVAC Equipment Rebate Savings Calculator
Read Next
Study Time Planner Authority Network America › Life Services Authority › National Calculator Authority .calc-container { max-width: 640px;...