Resources
Lighting Tools
Beam Width
17' 9"
17.74 ft
Throw Distance
40' 0"
40.00 ft
Center Lux
—
Beam Placement
ft
m
Beam width = 2 × throw × tan(beam angle ÷ 2) · Drag the ● handle to aim the centerline.
Fixture Reference
Beam Angle—
Power—
Type—
Rated Lux—
Lux @ Distance—
Weight—
Photometric Estimate
m
ft
Lux = rated lux × (rated distance in same unit as throw ÷ throw)² · Beam angle affects spread, not center intensity
Enter Any Two Values
Amber = your inputs · Blue = calculated. Fill two fields and the rest auto-fill. Hit Reset to start over.
Volts
Amps
Resistance
W = V × A · V = W ÷ A · A = W ÷ V · Ω = V ÷ A
Formula Reference
Watts (W)
W = V × A
W = V² ÷ Ω
W = A² × Ω
Volts (V)
V = W ÷ A
V = A × Ω
V = √(W × Ω)
Amps (A)
A = W ÷ V
A = V ÷ Ω
A = √(W ÷ Ω)
Resistance (Ω)
Ω = V ÷ A
Ω = V² ÷ W
Ω = W ÷ A²
The 80% rule: a breaker should not carry more than 80% of its rated ampacity continuously (NEC §210.19). Example: a 20A breaker → max continuous load 16A.
Resistor Color Code Decoder
Select each color band left to right, starting from the end with bands closest together. Or type a value below to see the bands.
Resistance
100 Ω
Tolerance: ±5%
Ohms
100 Ω
Enter a Value → See Bands
Read from the end where bands are closest together · Gold/Silver band is always tolerance (last band)
LED Current-Limiting Resistor
Calculate the resistor needed to safely limit current to an LED from a known supply voltage.
V
V
mA
R = (Vs − Vf) ÷ If · P = If² × R · Always use a resistor rated at 2× calculated wattage minimum
Color Band Reference
Read from the end with bands closest together. The last band (gold/silver) is always tolerance.
Black0 ×1
Brown1 ×10 ±1%
Red2 ×100 ±2%
Orange3 1k
Yellow4 10k
Green5 100k ±0.5%
Blue6 1M ±0.25%
Violet7 10M ±0.1%
Grey8 — ±0.05%
White9 —
Gold— ×0.1 ±5%
Silver— ×0.01 ±10%
4-band: digit · digit · multiplier · tolerance
5-band: digit · digit · digit · multiplier · tolerance
E.g. Brown–Black–Red–Gold = 1–0–×100–±5% = 1kΩ ±5%
80% Rule:per NEC §210.19, a breaker should not carry more than 80% of its rated ampacity continuously. A 20A breaker → 16A max continuous load.
5-band: digit · digit · digit · multiplier · tolerance
E.g. Brown–Black–Red–Gold = 1–0–×100–±5% = 1kΩ ±5%
80% Rule:per NEC §210.19, a breaker should not carry more than 80% of its rated ampacity continuously. A 20A breaker → 16A max continuous load.
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Polar Intensity Diagram
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