Star-Delta (Y-Δ) Conversion Calculator

What this tool does

Any three-terminal network of resistors can be redrawn as a star or as a delta, and swapping between the two often turns an unsolvable bridge circuit into a simple series-parallel one. For a balanced load, the star value is exactly one third of the delta value — which is also why a star-delta motor starter draws a third of the current.

Formula

R_Y = R_Δ ÷ 3 (balanced loads)

Variables

Worked example

Limitations

• Electrical installations are governed by national wiring rules. Cable sizing also depends on installation method, grouping, ambient temperature and protection devices, which this calculator does not evaluate.
• The calculation runs at full precision and only the display is rounded. If you copy an intermediate value and retype it, small differences can appear.