Lighting & Photometry Calculators
Free, practical tools for anyone working with light — convert between lumens, lux, candela, and watts, size a room's lighting, project brightness over distance, and cost out an LED switch.
Lumens ↔ Lux Calculator
Convert total light output (lumens) to the brightness landing on a surface (lux) for a room's area — and back the other way to find the output you need.
Watts to Lumens Calculator
Estimate a bulb's brightness from its wattage and luminous efficacy, with LED, CFL, halogen, and incandescent presets and the equivalent wattage of each.
Room Lighting Requirement Calculator
Size a room's lighting from its floor area and the recommended lux for the task — total lumens needed and how many bulbs it takes.
Candela ↔ Lumens Calculator
Move between luminous intensity (candela) and total beam output (lumens) using the beam angle — the link a spotlight or torch spec depends on.
Lux at Distance Calculator
Apply the inverse-square law to find the illuminance a source casts at a distance, and the distance at which it reaches a target lux.
LED Energy Savings Calculator
Compare the yearly energy and cost of an LED against an old incandescent or halogen bulb, scaled by how many bulbs you swap and for how long.