Contrast tools

#000000
|
rgb(0, 0, 0)
Contrast value

45.29 Lc

#cc7e23
|
rgb(204, 126, 35)
Sample text
Share these colors

APCA and WCAG 3.0

The Advanced Perception of Color Algorithm (APCA) considers the context in which colors are used to determine their readability. Font size, font weight, and the sequence of background and text colors all impact the recommended contrast value (Lc) for text.

APCA was included in previous working drafts of the WCAG 3.0 text contrast guidelines . However, the W3C Editor's Draft of WCAG 3.0 from June 2nd, 2023 reverted all guidelines to "Placeholder" status and removed prior guideline content, including text contrast and APCA.

The proposed WCAG 3.0 ratings for text contrast were based on the proximity of a calculated contrast value to its target score on the APCA Lookup Table below.

Although APCA’s eventual role in WCAG 3.0 is unclear, the APCA Readability Criterion (ARC) is developing as an independent standard for visual contrast. You can learn more in the ARC public working draft .

APCA Lookup Table

Font weight
100200300400500600700800900
12px
X
X
X
X
X
14px
X
X
100P
    100P
      90P
        75P
          X
          X
          15px
          X
          X
          100P
            90P
              75P
                70+
                  X
                  X
                  16px
                  X
                  X
                  90P
                    75P
                      70+
                        60+
                          60
                            X
                            18px
                            X
                            100P
                              75P
                                70+
                                  60+
                                    55+
                                      55
                                        55
                                          21px
                                          X
                                          90P
                                            70P
                                              60+
                                                55+
                                                  50+
                                                  50
                                                  50
                                                  24px
                                                  X
                                                  75P
                                                    60+
                                                      55+
                                                        50+
                                                        45+
                                                        45
                                                        45
                                                        28px
                                                        X
                                                        100
                                                          70+
                                                            55+
                                                              50+
                                                              45+
                                                              43+
                                                              43
                                                              43
                                                              32px
                                                              X
                                                              90
                                                                65+
                                                                  50+
                                                                  45+
                                                                  43+
                                                                  40+
                                                                  40
                                                                  40
                                                                  36px
                                                                  X
                                                                  75
                                                                    60+
                                                                      45+
                                                                      43+
                                                                      40+
                                                                      38+
                                                                      38
                                                                      38
                                                                      42px
                                                                      70
                                                                        55
                                                                          43
                                                                          40
                                                                          38
                                                                          35
                                                                          35
                                                                          35
                                                                          48px
                                                                          60
                                                                            50
                                                                            40
                                                                            38
                                                                            35
                                                                            33
                                                                            33
                                                                            33
                                                                            60px
                                                                            55
                                                                              45
                                                                              38
                                                                              35
                                                                              33
                                                                              30
                                                                              30
                                                                              30
                                                                              72px
                                                                              50
                                                                              40
                                                                              35
                                                                              33
                                                                              30
                                                                              30
                                                                              30
                                                                              30
                                                                              96px
                                                                              45
                                                                              35
                                                                              33
                                                                              30
                                                                              30
                                                                              30
                                                                              30
                                                                              30

                                                                              Table key

                                                                              • N
                                                                                WCAG 3.0 Rating 4 - meets or exceeds the values on the APCA Lookup table
                                                                              • N
                                                                                Rating 3 - 1-4% below
                                                                              • N
                                                                                Rating 2 - 5-9% below
                                                                              • N
                                                                                Rating 1 - 10-15% below
                                                                              • N
                                                                                  Rating 0 - >15% below
                                                                                • NP
                                                                                  Preferred for blocks of text
                                                                                • N+
                                                                                  Add 15 Lc to use for blocks of text
                                                                                • Font weight 100 should be avoided
                                                                                • X
                                                                                  Prohibited except for decorative purposes
                                                                                • Use for copyright/by-line only

                                                                                Example font combinations & ratings

                                                                                14px/400
                                                                                Rating: 0
                                                                                16px/400
                                                                                Rating: 0
                                                                                16px/600
                                                                                Rating: 0
                                                                                24px/500
                                                                                Rating: 0
                                                                                30px/300
                                                                                Rating: 0

                                                                                Attributions

                                                                                SAPC & APCA were invented / developed by Andrew Somers, Senior Color Science Researcher at Myndex Technologies as part of the ongoing PerceptEx™ Perception Research Project.

                                                                                SAPC: S-LUV Advanced Perceptual Color — an appearance model for self-illuminated displays

                                                                                APCA: Advanced Perceptual Contrast Algorithm — a method for determining contrast to guide web-based design.

                                                                                APCA is derived from the SAPC model. APCA is a method for prediction pf suprathreshold visual contrast of text on displays. APCA results are intended to provide design guidance for best readability of web-based content.

                                                                                APCA DISCLAIMER

                                                                                APCA is intended solely for web-based content per the W3 WCAG 3.0 standards, and the web-content version is licensed to the W3 per their cooperative agreement. Use for other-than web-based-content is restricted and/or prohibited. APCA is a public beta, under active development. Prior written authorization is required for the use of SAPC or APCA in the context of, or in applications for, transportation, aerospace, medical, military, or where human safety is involved.

                                                                                #000000
                                                                                |
                                                                                rgb(0, 0, 0)
                                                                                Contrast value

                                                                                6.58:1

                                                                                #cc7e23
                                                                                |
                                                                                rgb(204, 126, 35)
                                                                                Sample text
                                                                                Share these colors

                                                                                Normal text

                                                                                WCAG 2.1 AA
                                                                                pass
                                                                                WCAG 2.1 AAA
                                                                                fail

                                                                                Large text

                                                                                Text that is 14pt (18.67px) and bold or any text bigger than 18pt (24px) is defined as large scale text.

                                                                                WCAG 2.1 AA
                                                                                pass
                                                                                WCAG 2.1 AAA
                                                                                pass