Estimate the correlated color temperature (CCT) of a color in kelvin using McCamy’s approximation from CIE chromaticity. Warm whites land near 2700K, daylight D65 at 6504K, cool sky light higher. CCT is defined for whites and near-whites — the tool says so when your color is too saturated for the number to mean much.
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Temperature: the physics behind “warm” and “cool”
Color temperature is a real temperature: heat an idealized object and it glows — deep red around 1000K, orange-white near 2700K, neutral white by 5500K, blue-white beyond 7000K. Light sources are graded by the temperature whose glow they resemble, and that number organizes photography, lighting design and display calibration. The everyday vocabulary inverts the physics — we call the low-kelvin end “warm” and the high-kelvin end “cool” — and the calculator translates between number and feeling.
How a color becomes kelvins
The color projects into CIE chromaticity (the xy diagram), and McCamy’s approximation converts its position relative to the blackbody curve into a correlated color temperature. The xy coordinates are shown alongside — partly for auditability, partly because they are the honest representation: CCT is meaningful only near the white line, and the calculator warns when your color is too saturated for the number to carry weight.
| Source | Approx. CCT |
|---|---|
| Candle flame | ≈ 1900 K |
| Incandescent bulb | ≈ 2700 K |
| Neutral studio light | ≈ 4000 K |
| Daylight (D65 standard) | 6504 K |
| Overcast sky | 7000–10000 K |
Where the number does work
Identifying the light in a photo from a should-be-white patch (then correcting white balance with knowledge instead of sliders); choosing bulbs that match a room’s intent; explaining why a “white” label looks cream on one screen and icy on another; and sanity-checking near-neutrals in a palette — a background that reads 5000K sits differently than one at 7500K, even when both pass for white in isolation.
Limits, stated plainly
McCamy is an approximation (excellent near the white line, loose at the edges), CCT compresses a two-dimensional chromaticity into one number (a greenish and a pinkish white can share a CCT — that difference is the “tint” axis photographers know), and saturated colors are outside the concept’s jurisdiction entirely. The calculator says so rather than printing confident nonsense.
The tint axis: what CCT cannot say
CCT locates a white along the orange-to-blue axis; the perpendicular axis — green-to-magenta deviation from the blackbody line, called tint or Duv — is the other half of white-balance reality. Two 4000K sources can differ visibly: one sitting slightly green (typical of older fluorescents), one magenta-leaning. This page’s xy coordinates carry that information implicitly (distance from the blackbody locus), and photographers will recognize the pairing from their raw editors’ two sliders. When a white looks off despite a plausible CCT, the tint axis is where to look.
How to use the Color Temperature Calculator
- Pick or enter the color – near-whites give the most meaningful readings.
- Read the kelvin estimate, its warm/neutral/cool label and the CIE chromaticity.
- Mind the caveat notes for saturated colors.
Frequently asked questions
What does a color temperature in kelvin actually mean?
The temperature an idealized glowing object (blackbody) would need to emit light of that chromaticity: candle flames around 1900K look orange, incandescent bulbs 2700K, daylight D65 is defined at 6504K, blue sky reads 8000K+. Lower = warmer-looking, higher = cooler – yes, the naming is backwards from physics.
How is CCT estimated here?
Via McCamy's formula from CIE 1931 xy chromaticity – the standard quick approximation, dependable within roughly 2000-12500K for colors near the white line. The tool shows the xy coordinates too so the estimate is auditable.
Why does the tool warn me about my saturated color?
Because correlated color temperature is defined for near-whites. A saturated green is simply not on the blackbody line, and its "CCT" is a projection with limited meaning. The warning fires above moderate saturation instead of letting the number mislead.
What is the 2700K vs 4000K vs 6500K choice in lighting?
The household trilogy: 2700K warm white (living spaces), 4000K neutral (kitchens, offices), 6500K daylight (task lighting, matching screens). Enter a photo's white patch here to identify which family lit the scene.
How does this relate to a monitor's white point?
sRGB standardizes D65 – this calculator reads #ffffff as ~6500K by construction. A "warmer" screen profile literally moves the white point to lower kelvin; night-mode filters push 3400K and below.
Can I use this for photography white balance?
For diagnosis, yes: sample a should-be-neutral area and the kelvin estimate tells you which way the cast leans. Correction happens in your raw editor, but knowing "this is 3200K tungsten" is the actionable half.
Why do warm colors feel warm psychologically?
The association is embodied – fire and sunlight are literally warm and orange, overcast sky cold and blue. Design uses the shorthand: warm palettes read cozy and organic, cool ones clean and technical. The calculator quantifies which side a near-neutral leans.
