Extraction Rate Calculator

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Extraction Rate Calculator for Ventilation :root { –primary-color: #2c3e50; –accent-color: #3498db; –bg-color: #f4f7f6; –text-color: #333; –border-radius: 8px; } body { font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif; line-height: 1.6; color: var(–text-color); background-color: var(–bg-color); margin: 0; padding: 20px; } .container { max-width: 800px; margin: 0 auto; background: #fff; padding: 40px; border-radius: var(–border-radius); box-shadow: 0 4px 6px rgba(0,0,0,0.1); } h1, h2, h3 { color: var(–primary-color); } .calculator-box { background-color: #eef2f5; padding: 30px; border-radius: var(–border-radius); border: 1px solid #dce4e8; margin-bottom: 40px; } .form-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 20px; } .form-group { margin-bottom: 15px; } .form-group.full-width { grid-column: 1 / -1; } label { display: block; margin-bottom: 8px; font-weight: 600; color: var(–primary-color); } input[type="number"], select { width: 100%; padding: 12px; border: 1px solid #ccc; border-radius: 4px; font-size: 16px; box-sizing: border-box; } button.calc-btn { background-color: var(–accent-color); color: white; border: none; padding: 15px 30px; font-size: 18px; font-weight: bold; border-radius: 4px; cursor: pointer; width: 100%; transition: background-color 0.3s; margin-top: 10px; } button.calc-btn:hover { background-color: #2980b9; } #result-area { margin-top: 25px; padding: 20px; background-color: white; border-left: 5px solid var(–accent-color); display: none; } .result-value { font-size: 28px; font-weight: bold; color: var(–accent-color); } .result-label { font-size: 14px; color: #666; text-transform: uppercase; letter-spacing: 1px; } .error-msg { color: #e74c3c; font-weight: bold; margin-top: 10px; display: none; } .article-content { margin-top: 40px; border-top: 1px solid #eee; padding-top: 20px; } @media (max-width: 600px) { .form-grid { grid-template-columns: 1fr; } }

Extraction Rate Calculator

Calculate the required airflow capacity for extractor fans (hoods, bathroom fans) based on room dimensions and usage.

Kitchen (10 ACH) Commercial Kitchen (15 ACH) Bathroom / Shower (8 ACH) Utility Room (4 ACH) Living / Dining Room (6 ACH) Bedroom (2 ACH) Custom ACH…
Please enter valid dimensions.
Room Volume
0 m³
Target Air Changes
0 per hr
Required Extraction Rate
0 m³/hr
(approx. 0 Liters per second)

About Extraction Rate Calculation

Choosing the correct size extractor fan is critical for maintaining healthy air quality in your home or commercial space. The Extraction Rate refers to the volume of air a fan can move within a specific timeframe, typically measured in cubic meters per hour (m³/hr) or liters per second (l/s).

The Logic: Air Changes Per Hour (ACH)

The calculation relies on the concept of Air Changes Per Hour (ACH). This metric defines how many times the entire volume of air in a room needs to be replaced with fresh air every hour to prevent moisture buildup, odors, and mold growth.

Different rooms have different regulatory and practical standards for ACH:

  • Kitchens: High humidity and odors require 10 to 15 air changes per hour.
  • Bathrooms: require roughly 6 to 10 changes to evacuate steam effectively.
  • Utility Rooms: require roughly 4 changes per hour.
  • Living Areas: generally require fewer changes, around 2 to 6 per hour.

How to Calculate Extraction Rate

The formula for calculating the required extraction rate is straightforward physics based on fluid dynamics in a contained space:

Extraction Rate (m³/hr) = Room Volume (m³) × Air Changes Per Hour (ACH)

Step-by-Step:

  1. Calculate Volume: Multiply Length × Width × Height of the room in meters.
  2. Identify ACH: Select the required Air Changes Per Hour based on the room type (e.g., 10 for a kitchen).
  3. Multiply: Multiply the volume by the ACH to get the minimum m³/hr rating required for your fan.

Why Size Matters

If your extraction rate is too low, humidity will linger, leading to condensation on windows, damp walls, and potential mold issues. If the rate is significantly too high for the space without adequate intake ventilation, it can create negative pressure, causing doors to slam or drafts to be pulled in through cracks.

// Handle Custom ACH visibility document.getElementById('roomType').onchange = function() { var style = this.value === 'custom' ? 'block' : 'none'; document.getElementById('customAchGroup').style.display = style; }; function calculateExtractionRate() { // Get Inputs var length = parseFloat(document.getElementById('roomLength').value); var width = parseFloat(document.getElementById('roomWidth').value); var height = parseFloat(document.getElementById('roomHeight').value); var achSelect = document.getElementById('roomType').value; var ach = 0; // Handle ACH logic if (achSelect === 'custom') { ach = parseFloat(document.getElementById('customAch').value); } else { ach = parseFloat(achSelect); } // Error Handling var errorDiv = document.getElementById('error-message'); var resultDiv = document.getElementById('result-area'); if (isNaN(length) || isNaN(width) || isNaN(height) || length <= 0 || width <= 0 || height <= 0 || isNaN(ach)) { errorDiv.style.display = 'block'; resultDiv.style.display = 'none'; return; } // Logic Calculation errorDiv.style.display = 'none'; // 1. Calculate Volume in cubic meters var volume = length * width * height; // 2. Calculate Required Rate (m3/hr) var extractionRateM3 = volume * ach; // 3. Convert to Liters per Second (l/s) // 1 m3/hr = 0.277778 l/s var extractionRateLps = extractionRateM3 * 0.277778; // Display Results resultDiv.style.display = 'block'; document.getElementById('resVolume').innerHTML = volume.toFixed(2) + ' m³'; document.getElementById('resAch').innerHTML = ach; document.getElementById('resRate').innerHTML = Math.ceil(extractionRateM3) + ' m³/hr'; document.getElementById('resLps').innerHTML = Math.ceil(extractionRateLps); }

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