Create a professional panel schedule: Demand, kVA, Current, Auto cable size (Cu/Al), Voltage Drop (R+X), Derating, and Breaker sizing.
| # | Description | Load / Current | Unit | Type | Phase | DF | PF | Length (m) | Conductor | Cable (Auto) | Ampacity (A) | Derated (A) | Demand kW | kVA | Current (A) | VD Limit (%) | VD (%) | Breaker (A) | Status | Del |
|---|
Normal sizes the breaker on the load current itself (×1.0).
Continuous — a load running at full output for three hours or more — uses ×1.25.
Motor uses ×2.5 for starting, and the cable is sized on 1.25 × FLC because the
overload relay, not the breaker, protects the cable.
Voltage, PF, and Phase.
A measured current is already a demand current, so DF is locked at 1.00 — otherwise the kW summary and the phase
currents would describe two different loads. For normal design work, keep Unit as kW / HP / kVA / W.
HP × 0.746 ÷ Motor Efficiency, because HP is shaft output and the cable has to carry the
electrical input. At 0.90 efficiency that is about 11% more current than the shaft figure.
3P rows use the L-L voltage; 1P — R/Y/B rows use the L-N voltage and land on that phase in the R/Y/B summary (like a real panel schedule).
1P (Auto) distributes single-phase rows across R → Y → B automatically.
This tool helps you create an electrical panel schedule and quickly estimate demand load, kVA, current, auto cable size (Copper/Aluminum), voltage drop, derated ampacity, and breaker sizing. It is designed for fast checks during design coordination, estimating, and site verification.
A panel schedule is a circuit list showing connected load, demand factors, protective device size, and cable details. It is used for load balancing (R/Y/B), feeder sizing, and verifying voltage drop and ampacity compliance.
Switching the standard updates typical voltage presets and cable tables used for auto-selection.
VD Limit (%) is the maximum allowed voltage drop percentage. The tool compares calculated VD (%) to the limit. Typical targets: 3% for branch circuits and 5% total (feeder + branch) for overall system design.
Cable tables show a base ampacity at standard reference conditions. Real projects need derating due to temperature, installation method, and grouping. The tool applies:
Derating is applied before cable selection — the auto-selected cable already accounts for temperature, installation method and grouping. Ambient temperature is conservatively rounded up to the next band (32°C uses the 35°C factor, not 30°C), and above 55°C the tool stops rather than guessing, because that is where the published table ends and most PVC-insulated cable is out of its rating anyway.
Installation factors are applied as reductions only. Free air is treated as 1.00, not as an uplift — a base table is tied to its own reference method, and multiplying it upward for free air would claim ampacity the table never certified. Where free-air ratings genuinely matter, take them from the manufacturer's free-air column.
The breaker is snapped to standard steps for the selected standard — IEC (16A, 32A, 63A, 125A…) or NEC (15A, 30A, 60A, 70A, 90A, 110A…). The cable is then coordinated with the breaker: for normal and continuous loads the derated ampacity must be ≥ the breaker rating (the IEC rule Ib ≤ In ≤ Iz); for motors the cable is sized for 1.25 × FLC, since the overload relay — not the 2.5× breaker — protects the cable. The tool also auto-upsizes the cable until the voltage drop is within your VD Limit.
A normal load is sized on its own current with no uplift. A continuous load — one running at full output for three hours or more, such as lighting or a compressor — is sized at 1.25 × its current. A motor is sized at 2.5 × full load current so the breaker rides through starting, while its cable is sized on 1.25 × FLC because the overload relay protects the cable.
Select it when you have a measured current value (site test / clamp meter) and you want to check cable size, voltage drop, and breaker selection. The demand factor is locked at 1.00 in this mode, because a measured current already is the demand current — applying a factor to the kW while leaving the current untouched would make the summary and the phase totals disagree. For design stage loads, use kW/HP/kVA/W instead.
Ampacity (A) is the base cable rating from the table. Derated (A) applies temperature, installation method, and grouping factors. The tool uses Derated (A) for the pass/fail check.
The tool automatically upsizes the cable until voltage drop is within your VD Limit (%) — so “VD HIGH” now means even the largest cable in the table cannot meet the limit. Solutions: reduce the run length, use parallel runs, raise the panel voltage level, relax the VD limit, or move the panel closer to the load.
Sum each circuit's connected load and apply its demand factor (Demand kW = Connected kW × DF). Convert to current using the phase voltage and PF — 3-phase rows use the L-L voltage with the √3 formula, 1-phase rows use the L-N voltage. Balance single-phase circuits across R/Y/B; the panel feeder is sized on total demand kVA and the worst phase current.
IEC practice covers 230/400/415V 50Hz systems worldwide with mm² conductors and 16/32/63A breaker steps. NEC covers 120/208/277/480V 60Hz systems in USA/Canada with AWG/kcmil conductors and 15/30/60A breaker steps. Switching the standard changes the voltage presets, cable tables and breaker steps automatically.