Field Calculator
Instant calculations for job-site decisions: circuit sizing, wire selection, speaker wiring, cable distances, and 70V distributed audio. No internet required.
⚡
Circuit Load Calculator
Watts → Amps → Breaker size (NEC 80% rule)
🔌
Wire Gauge Selector
Find the right AWG for your run length and load
Quick Reference
AWG
Max A
Common Use
#14
15A
Most residential 15A circuits
#12
20A
Standard 20A kitchen/bath circuits
#10
30A
30A circuits, small HVAC, hot tubs
#8
40A
40A circuits, ranges, dryers
#6
55A
50-60A, large HVAC, EV chargers
#4
70A
70A subpanels, large equipment
#2
95A
Large subpanels, service entrance
🔊
Speaker Impedance Calculator
Series and parallel zone impedance — verify amp safety
Spk 1
Spk 2
Combined Load
4.0 Ohm
Amp Minimum
4 Ohm
Status
Safe
Parallel: 1/R_total = 1/R1 + 1/R2 + ... | Series: R_total = R1 + R2 + ...
🌐
Cable Run Length Reference
Check which standards your run length supports
Standard
Max (ft)
Notes
Cat5e 1GbE
328
1000BASE-T — standard AV VLAN drop
Cat6 1GbE
328
Lower crosstalk, better for high-density
Cat6A 10GbE
328
Required for 10G to WAPs or cameras
PoE / PoE+
328
IEEE 802.3af/at — same cable limit as data
HDBaseT 4K
328
100m max, no boosters; use for AV matrix
HDMI passive
16
Typical ~5m; quality cables reach ~10m
HDMI active
50
Active optical cable — up to 100m possible
RS-232 serial
50
EIA-232 spec; use RS-485 for longer runs
RS-485 serial
3,937
Multi-drop bus; Lutron QSX, many DSPs
IR emitter
98
30m typical; use IR Xtender for longer
📢
70V Speaker Tap Calculator
Distributed audio load balancing — verify amp tap budget before wiring
Tap Load: 10W (10%)Safe limit: 80W
0W80%100W
Speaker / ZoneTap WattageCoverage Est.Xfmr Impedance
~300 sq ft
1250 Ω
~200 sq ft
2500 Ω
~300 sq ft
1250 Ω
Total Tapped
10W
Amp Load
10%
Remaining
90W
Speakers
3
70V Rule: Never exceed 80% of amp rated output. Each speaker tap is stepped down from 70.7V via transformer — tap wattage is independent of 8Ω speaker impedance. Coverage tip: 4W taps give ~300 sq ft in commercial ceilings (9–10 ft); 2W taps for corridors and small offices; 8W for large open spaces. Impedance: Z = 5000 / tap_watts (at 70.7V). Use this to verify transformer specs on the data sheet.