Lighting Calculator

  • Maximum Lights per Circuit Calculator
    Find how many light fixtures you can safely put on a circuit. Enter voltage, breaker amps and watts per fixture to get the max count at the 80% rule.
  • Projector Screen Size Calculator
    Convert a diagonal screen size and aspect ratio into exact width, height and area in inches and centimeters for projectors and TVs.
  • Number of Bulbs Needed for a Room Calculator
    Find how many light bulbs you need for a room. Enter room area, desired light level, and lumens per bulb to get the count.
  • Lighting Watts to Amps Calculator
    Convert lighting watts to amps instantly. Enter total fixture wattage, voltage, and power factor to find the current draw for sizing circuits and breakers.
  • Foot-Candles to Lux Calculator
    Convert foot-candles (fc) to lux (lx) instantly. Enter an illuminance value and get the exact result using lux = fc × 10.7639.
  • Lux to Foot-Candles Calculator
    Convert lux to foot-candles instantly. Enter an illuminance value in lux and get the equivalent foot-candles using fc = lux / 10.7639.
  • LED Current Limiting Resistor Calculator
    Calculate the series resistor needed to safely drive an LED. Enter supply voltage, LED forward voltage, and current to get resistance and power rating.
  • Christmas String Light Count Calculator
    Find how many Christmas string lights you need to cover a given length and the total wattage they draw. Quick holiday lighting planner.
  • LED Bulb Lifespan Calculator
    Convert an LED bulb's rated lifespan in hours into years based on daily usage. Find out how long your LED bulbs will really last.
  • LED Savings Calculator
    Calculate how much money you save each year by switching from incandescent or halogen bulbs to energy-efficient LED lighting.
  • TV/Projector Viewing Distance Calculator
    Find the ideal TV or projector viewing distance from screen diagonal, aspect ratio, and preferred viewing angle (SMPTE 30°, THX 40°).
  • Projector Brightness (Nits / Foot-Lamberts) Calculator
    Calculate projector screen brightness in foot-lamberts (fL) and nits from lumens, screen gain, and screen size. Free, instant home-theater tool.
  • Average Illuminance Calculator
    Calculate average illuminance (lux) from light fixtures using the lumen method: fixtures, lumens, coefficient of utilization, light loss factor and area.
  • Lux to PPFD Conversion Calculator
    Convert lux to PPFD (µmol/m²/s) using source-specific conversion factors for sunlight, LED, HPS and more. Free grow-light photosynthetic light estimator.
  • 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 Wire Voltage Drop Calculator
    Calculate the voltage drop in wires feeding an LED or LED strip. Enter current, length, wire area and material to find loss, voltage at the LED and power waste.
  • 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.
  • 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.
  • 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.
  • 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.
  • Recessed Lighting Spacing Calculator
    Input room size, ceiling height, target foot‑candles, and lumens per fixture to get recessed light count and recommended spacing.
  • 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.
  • 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.

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