CFM per Room Calculator
ANA›Life Services Authority›National Calculator Authority›CFM per Room 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; } }
CFM per Room Calculator
Calculate the required CFM (Cubic Feet per Minute) of airflow needed for a room based on its length, width, ceiling height, and desired air changes per hour (ACH).
Room Length (ft)
Room Width (ft)
Ceiling Height (ft)
Air Changes per Hour (ACH)
Typical: Bedroom 4–6, Living Room 4–6, Kitchen 7–8, Bathroom 6–8, Office 4–6
Calculate
function cfmCalc() { var resultDiv = document.getElementById("cfm-result"); resultDiv.style.display = "none"; resultDiv.className = "calc-result";
var length = parseFloat(document.getElementById("cfm-length").value); var width = parseFloat(document.getElementById("cfm-width").value); var height = parseFloat(document.getElementById("cfm-height").value); var ach = parseFloat(document.getElementById("cfm-ach").value);
// --- Validation --- var errors = []; if (isNaN(length) || length 0) { resultDiv.className = "calc-result calc-error"; resultDiv.innerHTML = "Please fix the following:" + errors.map(function(e){ return ""; }).join("") + ""; resultDiv.style.display = "block"; return; }
// --- Formula --- // Room Volume (ft³) = Length × Width × Height // CFM = (Room Volume × ACH) / 60 var volume = length * width * height; var cfm = (volume * ach) / 60;
// Additional useful outputs var cfmPerSqFt = cfm / (length * width);
resultDiv.innerHTML = "### Results " + "" + "Room Volume" + "" + volume.toFixed(1) + " ft³" + "Required CFM" + "" + cfm.toFixed(1) + " CFM" + "CFM per sq ft" + "" + cfmPerSqFt.toFixed(2) + " CFM/ft²" + "Air Changes per Hour" + "" + ach.toFixed(1) + " ACH" + "";
resultDiv.style.display = "block"; }
#### Formula
Step 1 — Room Volume (ft³):
Volume = Length × Width × Ceiling Height
Step 2 — Required CFM:
CFM = (Volume × ACH) / 60
Where ACH is Air Changes per Hour — the number of times the entire air volume of the room is replaced in one hour. Dividing by 60 converts from cubic feet per hour to cubic feet per minute.
Example: A 15 ft × 12 ft room with an 8 ft ceiling and 6 ACH: Volume = 15 × 12 × 8 = 1,440 ft³ CFM = (1,440 × 6) / 60 = 144 CFM
#### Assumptions & References
- All room dimensions are entered in feet; the result is in CFM (Cubic Feet per Minute).
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Recommended ACH values vary by room type (ASHRAE Standard 62.1):
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This calculator provides a baseline estimate. Actual HVAC design should account for heat loads, humidity, occupancy, and local building codes.
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