Bonding Jumper Sizing Reference
Look up a main, system, or supply-side bonding jumper from ungrounded conductor size, material, and parallel raceway arrangement.
Bonding jumper details
Use one set for this arrangement.
Minimum bonding jumper size
About this reference
Use the inputs to look up a minimum conductor size for a main bonding jumper, system bonding jumper, or supply-side bonding jumper. The result is based on the largest ungrounded conductor or the equivalent area of parallel conductors.
Method and assumptions
For separate parallel raceways, the individual-per-raceway option sizes each jumper from the conductor set in that raceway. The common-jumper option sums the largest ungrounded conductor areas from all parallel sets before selecting one jumper. A single conductor set uses the selected conductor size directly.
When the equivalent area exceeds the listed copper or aluminum range, the calculator applies the 12.5% area note and rounds up to a listed conductor size. This screen does not make the installation compliant by itself.
FAQs
What does this reference size?
It applies the alternating-current table basis for a main bonding jumper, system bonding jumper, or supply-side bonding jumper. The load-side equipment bonding jumper uses a different equipment grounding conductor basis.
How should I handle parallel raceways?
Select an individual jumper in each raceway when each raceway is bonded separately. Select one common jumper when a single jumper bonds the parallel raceways and the table basis uses the sum of the largest ungrounded conductors from the parallel sets.
What happens above the table range?
The calculator applies the 12.5% area note to the largest conductor or equivalent parallel area, then rounds up to the next listed conductor size. Material-equivalency requirements and installation-specific rules still need a separate review.
Sources
- NFPA 70, National Electrical Code, 2026 edition — Article 270.102 and Table 270.102(C)(1) are the supply-side, main, and system bonding-jumper sizing basis used here; confirm the adopted final edition and local amendments.
- NFPA Code-Making Panel 5 Second Draft Report, preliminary report — public code-development material for grounding and bonding provisions; it is not a substitute for the adopted final text.