Crop Factor & Equivalent Focal Length Calculator
ANA›Life Services Authority›National Calculator Authority›Crop Factor & Equivalent Focal Length 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; } }
Crop Factor & Equivalent Focal Length Calculator
Calculate the crop factor of a camera sensor and find the equivalent focal length relative to a full-frame (35mm) sensor.
Calculation Mode
Equivalent Focal Length (Lens FL × Crop Factor) Crop Factor from Sensor Dimensions Native Focal Length from Equivalent FL
Native (Actual) Focal Length (mm)
Crop Factor
Common values: Full-frame = 1.0, APS-C Nikon/Sony = 1.5, APS-C Canon = 1.6, Micro 4/3 = 2.0
Sensor Width (mm)
Sensor Height (mm)
Native (Actual) Focal Length (mm) (optional)
Desired Equivalent Focal Length (mm)
Crop Factor
Calculate
function croToggleMode() { var mode = document.getElementById('cro-mode').value; document.getElementById('cro-mode-equiv').style.display = (mode === 'equiv') ? '' : 'none'; document.getElementById('cro-mode-crop').style.display = (mode === 'crop') ? '' : 'none'; document.getElementById('cro-mode-reverse').style.display = (mode === 'reverse') ? '' : 'none'; document.getElementById('cro-result').innerHTML = ''; }
function croCalc() { var resultDiv = document.getElementById('cro-result'); var mode = document.getElementById('cro-mode').value;
// Full-frame sensor diagonal (35mm standard): 43.2666 mm // Width = 36 mm, Height = 24 mm → diagonal = sqrt(36²+24²) = 43.2666 mm var FF_DIAG = Math.sqrt(3636 + 2424); // 43.2666...
if (mode === 'equiv') { var nativeFL = parseFloat(document.getElementById('cro-native-fl').value); var cropF = parseFloat(document.getElementById('cro-crop-factor-input').value);
if (isNaN(nativeFL) || nativeFL Please enter a valid native focal length (> 0 mm).'; return; } if (isNaN(cropF) || cropF Please enter a valid crop factor (> 0).'; return; }
var equivFL = nativeFL * cropF; var angleOfView = 2 * Math.atan(43.2666 / (2 * equivFL)) * (180 / Math.PI);
resultDiv.innerHTML = '### Results ' + '' + 'Native Focal Length' + nativeFL.toFixed(1) + ' mm' + 'Crop Factor' + cropF.toFixed(2) + 'x' + 'Equivalent Focal Length (35mm)' + equivFL.toFixed(1) + ' mm' + 'Approx. Diagonal Angle of View' + angleOfView.toFixed(1) + '°' + '' + 'A ' + nativeFL.toFixed(1) + ' mm lens on a ' + cropF.toFixed(2) + 'x crop sensor behaves like a ' + equivFL.toFixed(1) + ' mm lens on a full-frame camera.
';
} else if (mode === 'crop') { var sw = parseFloat(document.getElementById('cro-sensor-w').value); var sh = parseFloat(document.getElementById('cro-sensor-h').value); var nativeFL2 = parseFloat(document.getElementById('cro-native-fl-2').value);
if (isNaN(sw) || sw Please enter a valid sensor width (> 0 mm).'; return; } if (isNaN(sh) || sh Please enter a valid sensor height (> 0 mm).'; return; }
var sensorDiag = Math.sqrt(swsw + shsh); var cropFactor = FF_DIAG / sensorDiag;
var html = '### Results ' + '' + 'Sensor Width' + sw.toFixed(2) + ' mm' + 'Sensor Height' + sh.toFixed(2) + ' mm' + 'Sensor Diagonal' + sensorDiag.toFixed(4) + ' mm' + 'Full-Frame Diagonal (reference)' + FF_DIAG.toFixed(4) + ' mm' + 'Crop Factor' + cropFactor.toFixed(4) + 'x' + '';
if (!isNaN(nativeFL2) && nativeFL2 > 0) { var equivFL2 = nativeFL2 * cropFactor; var aov2 = 2 * Math.atan(FF_DIAG / (2 * equivFL2)) * (180 / Math.PI); html += '' + 'Native Focal Length' + nativeFL2.toFixed(1) + ' mm' + 'Equivalent Focal Length (35mm)' + equivFL2.toFixed(1) + ' mm' + 'Approx. Diagonal Angle of View' + aov2.toFixed(1) + '°' + ''; }
resultDiv.innerHTML = html;
} else if (mode === 'reverse') { var equivFL3 = parseFloat(document.getElementById('cro-equiv-fl').value); var cropF3 = parseFloat(document.getElementById('cro-crop-factor-rev').value);
if (isNaN(equivFL3) || equivFL3 Please enter a valid equivalent focal length (> 0 mm).'; return; } if (isNaN(cropF3) || cropF3 Please enter a valid crop factor (> 0).'; return; }
var nativeFL3 = equivFL3 / cropF3; var aov3 = 2 * Math.atan(FF_DIAG / (2 * equivFL3)) * (180 / Math.PI);
resultDiv.innerHTML = '### Results ' + '' + 'Desired Equivalent Focal Length' + equivFL3.toFixed(1) + ' mm' + 'Crop Factor' + cropF3.toFixed(2) + 'x' + 'Required Native Focal Length' + nativeFL3.toFixed(1) + ' mm' + 'Approx. Diagonal Angle of View' + aov3.toFixed(1) + '°' + '' + 'To achieve a ' + equivFL3.toFixed(1) + ' mm full-frame equivalent on a ' + cropF3.toFixed(2) + 'x crop sensor, you need a ' + nativeFL3.toFixed(1) + ' mm lens.
'; } }
#### Formulas Used
Crop Factor from sensor dimensions: Crop Factor = FF_diagonal / Sensor_diagonal where FF_diagonal = √(36² + 24²) ≈ 43.267 mm (35mm full-frame standard) and Sensor_diagonal = √(width² + height²)
Equivalent Focal Length: EFL = Native_FL × Crop_Factor
Native Focal Length from Equivalent: Native_FL = EFL / Crop_Factor
Diagonal Angle of View: AoV = 2 × arctan(FF_diagonal / (2 × EFL))
#### Assumptions & References
- Reference: Ray, S.F. (2002). Applied Photographic Optics. Focal Press.
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