Lighting Calculator

  • Coefficient of Utilization (Lumen Method) Calculator
    Calculate how many light fixtures you need using the lumen method with coefficient of utilization (CU) and light loss factor (LLF).
  • Lumens to Candela Calculator
    Convert lumens to candela using the beam apex angle. Free lumens-to-candela calculator with solid angle output, formula, and a worked example.
  • Beam Angle to Spot Diameter Calculator
    Calculate the spot (beam) diameter of a light fixture from its beam angle and distance. Find spot size, radius and illuminated area instantly.
  • Candela to Lumens Calculator
    Convert candela (cd) to lumens (lm) using luminous intensity and beam apex angle. Free, accurate candela-to-lumens converter with solid angle output.
  • Watts to Lumens Calculator
    Convert watts to lumens instantly. Enter power in watts and luminous efficacy (lm/W) to find the light output in lumens for LED, CFL or incandescent bulbs.
  • Light Bulb Energy Cost Calculator
    Calculate the yearly, monthly and daily electricity cost of running a light bulb from its wattage, hours used per day and your price per kWh.
  • PPFD to DLI Calculator
    Convert PPFD (µmol/m²/s) to DLI (mol/m²/day) using your grow light's intensity and daily photoperiod. Free, instant grow-light calculator.
  • Inverse Square Law Light Intensity Calculator
    Calculate light intensity at a new distance using the inverse square law E₂ = E₁ × (d₁/d₂)². Free physics & lighting tool for lux and illuminance.
  • Luminous Efficacy Calculator
    Calculate luminous efficacy in lumens per watt (lm/W) from a light source's luminous flux and electrical power. Fast, free, and accurate.
  • Lumens per Square Foot Calculator
    Calculate foot-candles (lumens per square foot) from total lumens and room area. Free lighting calculator with instant lux conversion.
  • Lux to Lumens Calculator
    Convert lux to lumens instantly. Multiply illuminance (lux) by the illuminated area in square metres to get total luminous flux in lumens.
  • Room Lighting Lumens Calculator
    Calculate how many lumens a room needs based on its size and lighting purpose. Enter length, width, and light level to get total lumens and bulb count.
  • Lumens to Lux Calculator
    Convert lumens to lux instantly. Enter luminous flux (lm) and the illuminated area in m² to find illuminance (lux = lumens ÷ area).
  • LED Strip Power Supply Calculator
    Calculate the right LED strip power supply (PSU) wattage and current. Enter watts per meter, length and voltage to size a driver with safety headroom.
  • Ceiling Fan Size Calculator
    Find the right ceiling fan blade span for your room. Enter length and width to get a recommended fan size in inches based on room area.
  • LED Strip Length, LED Count & Power Draw Calculator
    Calculate LED strip power draw, total LED count and current. Enter strip length, LEDs per meter, watts per LED and voltage to size your power supply.
  • Projector Throw Distance Calculator
    Calculate how far to place your projector from the screen using its throw ratio and screen width. Get distance in inches, feet, and meters instantly.
  • Illuminance Unit Conversion Calculator
    Convert illuminance between lux, kilolux, phot, foot-candle, nox and lumen-per-area units instantly. Free universal physics unit converter.
  • Watts to Lux Calculator
    Convert watts to lux using luminous efficacy and lit area. Enter power (W), efficacy (lm/W) and area (m²) to get illuminance in lux instantly.
  • Incandescent vs CFL vs LED Bulb Running Cost Comparison (15-Year)
    Compare 15-year running cost (purchase + electricity) of incandescent, CFL and LED bulbs. Currency-agnostic; enter your local price and electricity rate.
  • LED Savings Calculator
    Calculate how much money you save each year by switching from incandescent or halogen bulbs to energy-efficient LED lighting.
  • Lumens to Watts Calculator
    Convert lumens to watts instantly. Enter luminous flux and luminous efficacy (lm/W) to find the electrical power a light source needs.
  • Daily Light Integral Calculator
    Calculate the Daily Light Integral (DLI) for plants from PPFD and photoperiod. Convert µmol/m²/s and light hours into mol/m²/day for grow lights.
  • Recessed Lighting Calculator
    Enter room length, width, ceiling height, and per‑fixture lumens to estimate how many recessed lights you need for comfortable, even lighting.

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