Is this window bright enough?
Window light planner
Learn if the spot works — and whether a grow light would help if it does not.
Loading calculator…
How to use this estimate
Arrange the room scene to match your setup, then read the plain-language verdict. Use Preview recommended placement to compare before and after. Technical measurements stay under “Why this recommendation?”
Common mistakes
- Treating the sun path as a precise solar simulation
- Measuring light at the fixture instead of at leaf height
- Ignoring curtains, trees, screens, and seasonal changes
- Assuming north and south windows behave the same in both hemispheres
Assumptions at a glance
Last reviewed with the calculator formula set on 2026-07-23. Estimates stay range-based on purpose.
Key sources and methodology details
- Indoor window orientation DLI estimate bands — Plant Light Planner planning heuristic. Reviewed 2026-07-26. https://extension.unh.edu/blog/2021/02/optimizing-plant-growth-indoor-lighting-qa
- Daily Light Integral from PPFD and photoperiod — University of New Hampshire Extension. Reviewed 2026-07-26. https://extension.unh.edu/resource/supplemental-lighting-run-time-worksheet
- Indoor plant light category DLI planning ranges — University of New Hampshire Extension (synthesized planning bands). Reviewed 2026-07-26. https://extension.unh.edu/blog/2021/02/optimizing-plant-growth-indoor-lighting-qa
Full portfolio methodology: Methodology
