Lighting Gel Color Temperature Calculator
Enter a fixture’s color temperature and the temperature you want to match, and get the mired shift plus a suggested correction gel strength.
Correction needed
How the calculator works
Color temperature in Kelvin doesn’t shift evenly under gel — the same physical filter produces a bigger Kelvin change on a cool source than a warm one. The mired scale (1,000,000 ÷ Kelvin) fixes that: gels shift color temperature by roughly the same number of mireds regardless of the starting point, which is why manufacturers rate their correction filters in mired shift rather than degrees Kelvin.
This tool converts both your source and target temperatures to mireds, takes the difference, and maps the size and direction of that shift onto the familiar full/half/quarter/eighth CTO or CTB strength scale.
Frequently Asked Questions
What is a mired shift?
A mired is 1,000,000 divided by the color temperature in Kelvin. Because color-correction gels shift color temperature by a roughly constant amount in mireds (not in Kelvin), gel manufacturers rate their filters in mired shift — this calculator converts your source and target Kelvin values into that unit for you.
What's the difference between CTO and CTB gel?
CTO (color temperature orange) warms a light down — lower Kelvin, more orange — and is used when your target is warmer than your source, for example correcting daylight through a window to match a tungsten fixture. CTB (color temperature blue) cools a light up — higher Kelvin, more blue — for the opposite case, like matching a tungsten fixture to daylight.
How accurate is the suggested gel strength?
The strength bands here are round, commonly used approximations of full/half/quarter/eighth correction strength. Manufacturers publish slightly different exact mired-shift values for their specific filters, so always check your gel swatch book or datasheet for the precise number before cutting gel for a real hang.
Why would I need to correct color temperature on stage at all?
Mixed sources are common in community theatre rigs — a few LED fixtures at one nominal Kelvin, older tungsten fresnels at another, and daylight leaking in from a window or door. Correcting the outliers toward a common target keeps skin tones and costume colors consistent across the stage instead of shifting warm-to-cool as an actor crosses.
Educational tool only. Strength bands are rounded approximations — check your gel manufacturer’s swatch book for the exact filter number before cutting gel.