Measure how different two colors really look. The calculator returns CIEDE2000 — the industry-standard perceptual difference, where roughly 1 is the threshold most people can notice — alongside the plain Lab distance (ΔE76), the WCAG contrast ratio and the per-axis L*, a*, b* deltas.
Generated locally in your browser — your colors, settings and code never leave this page.
Putting a number on “how different”
Disputes about whether two colors match are unwinnable by argument and trivial by measurement. ΔE (delta-E) is that measurement — the perceptual distance between two colors — and CIEDE2000 is its modern, industry-standard formulation, correcting the older formulas’ known distortions in saturated and dark regions. This calculator reports it alongside ΔE76 (the legacy straight-line Lab distance many instruments still quote), the WCAG contrast ratio, and the per-axis deltas that say not just how far apart, but in which direction.
The interpretation bands
Numbers need anchors. ΔE00 under 1: imperceptible to most observers side by side — the premium brand-match standard. 1–2: detectable on close inspection — typical commercial print tolerance. 2–5: visible but plausibly “the same color” in separated viewing — often acceptable across media. 5–10: clearly related, clearly different. Above 10: different colors, stop pretending. The calculator prints the applicable band with every result.
Direction matters too
The ΔL*, Δa*, Δb* rows turn a verdict into a correction: proof came back ΔL −3 (darker), Δa +2 (redder), Δb −1 (barely bluer) — now the fix is speakable. QC conversations that used to be “it looks off” become “bring lightness up three and pull the red”.
ΔE and contrast are different questions
The calculator shows both numbers because conflating them causes real mistakes. ΔE asks whether colors look alike; contrast asks whether one is readable on the other. Navy and gold: enormous ΔE, excellent contrast. Mid-blue and mid-red: enormous ΔE, terrible contrast. Match tolerance lives in ΔE; readability lives in the ratio; never let one answer the other’s question.
ΔE in purchasing and QA contracts
The number’s commercial life is worth knowing: print and manufacturing contracts routinely specify acceptance as a ΔE tolerance (“deliverables within ΔE00 2.0 of the reference”), turning color disputes into measurements. If you write or receive such clauses, two details matter — name the formula (ΔE00 and ΔE76 differ enough to change verdicts; this page shows both for exactly that reason) and name the measurement conditions, since instrument geometry and lighting move readings. The calculator handles the arithmetic half; the procedural half belongs in the contract language.
For screen-only work the same framing applies informally: a design system can declare “no two tokens within ΔE 2 of each other” (dedup rule) or “dark-mode translation must stay within ΔE 10 of brand hue” (identity rule) — house standards this page makes enforceable in seconds.
How to use the Color Difference Calculator
- Pick colors A and B.
- Read ΔE2000 with its plain-language verdict, plus ΔE76, WCAG contrast and per-axis deltas.
- Copy the report or JSON.
Frequently asked questions
What is a "good" ΔE2000 value?
Depends on the job: under 1 is imperceptible to most observers (premium brand matching), under 2 passes casual inspection (typical print tolerance), 2-5 is visible but arguably acceptable for screens, above 10 reads as a different color. The calculator prints these bands with your score.
Why are there two ΔE numbers, 2000 and 76?
ΔE76 is the original straight-line distance in Lab – simple but it overstates differences in saturated regions. CIEDE2000 adds weighting functions that match human judgment far better and is today's standard. Both are shown because older specs and instruments still quote 76.
How is ΔE different from the WCAG contrast ratio?
They measure different things: ΔE asks "do these look like the same color?", contrast asks "is one readable on the other?". Two colors can be wildly different (huge ΔE) yet equally bright (useless contrast). The calculator reports both so the right question gets the right number.
What do the Δa* and Δb* rows tell me?
The direction of the difference: positive Δa* means B is redder than A, negative greener; positive Δb* yellower, negative bluer; ΔL* lighter or darker. When a print proof comes back "off", these rows say off which way – actionable for correction.
Is ΔE symmetric – does the order of A and B matter?
CIEDE2000 is symmetric for all practical purposes and this implementation is verified against the published Sharma test pairs, including the tricky hue-rotation cases. Swap A and B and the score holds.
Can I use this to validate a color-accurate display or print?
It is the arithmetic half: measure or sample the reproduced color, enter both, read ΔE. The missing half is capture accuracy – a phone photo of a print adds its own cast. For contracts, use a colorimeter; for sanity checks, this is exactly the tool.
What ΔE can the human eye detect at best?
Under ideal side-by-side viewing, trained observers resolve ΔE ≈ 0.5-1. Separated in time or space, the threshold rises fast – which is why ΔE 2 "passes" in most real contexts. The verdict line encodes exactly this.
