With　the　increasing　understanding　of　light＇s　non-visual　impact　on　human　circadian　system,　applying　circadian　daylighting　in　buildings　becomes　attractive.　The　successful　adoption　of　circadian　daylighting　requires　a　considerable　amount　of　light　incident　at　the　eyes　without　causing　discomfort　glare.　Therefore,　developing　daylighting　strategies　that　can　efficiently　provide　indirect　corneal　illuminance　is　a　promising　approach.　An　equation　is　proposed　to　establish　the　dependence　of　daylight-enabled　corneal　illuminance,　especially　its　indirect　component,　on　room　surface　reflectance　and　window-to-wall　ratio　(WWR).　The　accuracy　of　the　equation　is　validated　in　an　artificial　sky　lab　which　mimics　a　fixed　overcast　sky　condition.　Experiments　using　scaled　room　models　with　various　combinations　of　interior　surface　reflectance,　WWRs,　testing　locations　and　measurement　directions　prove　that　the　proposed　equation　is　accurate.　The　results　suggest　that　room　surface　reflectance　plays　a　dominant　role　in　maximizing　indirect　corneal　illuminance.　This　is　further　confirmed　by　performing　a　Radiance　lighting　simulation　analysis　on　daylight-enabled　morning-hour　Circadian　Stimulus　in　a　classroom,　which　supports　the　proposed　equation　as　well.　This　work　concludes　that　the　proposed　equation　can　provide　quick　estimation　in　circadian　daylighting　design　and　that　high　room　surface　reflectance　is　the　key　to　achieve　efficient　and　quality　circadian　daylighting.　(C)　2020　Elsevier　B.V.　All　rights　reserved.