Irrigation Run Time Calculator
ANA›Life Services Authority›National Calculator Authority›Irrigation 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 Run Time Calculator
Calculate how long to run your irrigation system to apply a desired amount of water to your lawn or garden.
Desired Water Application (inches)
Sprinkler Precipitation Rate (inches/hour)
System Efficiency (%)
Calculate Fill in the fields above and click Calculate.
function irrCalc() { var resultDiv = document.getElementById('irrResult');
var desiredWater = parseFloat(document.getElementById('irrDesiredWater').value); var precipRate = parseFloat(document.getElementById('irrPrecipRate').value); var efficiency = parseFloat(document.getElementById('irrEfficiency').value);
// --- Validation --- if (isNaN(desiredWater) || desiredWater Please enter a valid desired water application (> 0 inches).'; return; } if (isNaN(precipRate) || precipRate Please enter a valid precipitation rate (> 0 inches/hour).'; return; } if (isNaN(efficiency) || efficiency 100) { resultDiv.innerHTML = 'Please enter a system efficiency between 1 and 100%.'; return; }
// --- Formula --- // Effective precipitation rate = precipRate * (efficiency / 100) // Run Time (hours) = desiredWater / effectivePrecipRate var efficiencyDecimal = efficiency / 100; var effectivePrecipRate = precipRate * efficiencyDecimal; var runTimeHours = desiredWater / effectivePrecipRate; var runTimeMinutes = runTimeHours * 60;
var hours = Math.floor(runTimeMinutes / 60); var minutes = Math.round(runTimeMinutes % 60);
var timeStr = ''; if (hours > 0 && minutes > 0) { timeStr = hours + ' hr ' + minutes + ' min'; } else if (hours > 0) { timeStr = hours + ' hr'; } else { timeStr = minutes + ' min'; }
resultDiv.innerHTML = 'Required Run Time: ' + runTimeMinutes.toFixed(1) + ' minutes (' + timeStr + ')' + 'Effective Precipitation Rate: ' + effectivePrecipRate.toFixed(3) + ' in/hr' + 'Water Applied per Hour (gross): ' + precipRate.toFixed(2) + ' in/hr' + 'System Efficiency: ' + efficiency + '%'; }
#### Formula
Effective Precipitation Rate (in/hr) = Precipitation Rate × (Efficiency / 100) Run Time (hours) = Desired Water Application (in) ÷ Effective Precipitation Rate (in/hr) Run Time (minutes) = Run Time (hours) × 60
Example: To apply 1.0 inch with a sprinkler rated at 1.5 in/hr and 75% efficiency: Effective Rate = 1.5 × 0.75 = 1.125 in/hr Run Time = 1.0 ÷ 1.125 = 0.889 hr ≈ 53.3 minutes
#### Assumptions & References
- The precipitation rate (also called application rate) is provided by the sprinkler manufacturer or measured via catch-cup test.
- System efficiency accounts for losses due to wind drift, evaporation, and uneven distribution. Typical values: rotary heads 75–85%, fixed spray heads 65–75%, drip systems 90–95%.
- A common lawn irrigation target is 1 inch per week, applied in 1–3 sessions to encourage deep root growth.
- Formula reference: Irrigation Association, Landscape Irrigation Scheduling and Water Management (2014).
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