Reference table
AWG Wire Resistance Table for Fire Alarm Circuits
Lookup copper conductor resistance values for fire alarm NAC and SLC voltage drop calculations using common AWG sizes.
AWG wire resistance table6 rows2 linked calculators
Rows
6
Reference values
Columns
2
Lookup fields
Linked tools
2
Calculators using this data
Page role
Use this page for a defined task before moving to the next project record.
- Audience
- Engineers, designers, reviewers, and technicians selecting calculator input values.
- Job
- Use this table when fire alarm voltage drop or circuit resistance needs conductor resistance by AWG size.
- Evidence
- Match AWG size and conductor material basis before using ohms per 1000 ft. Use one-way route length in calculators that explicitly compute round-trip resistance.
- Output
- Selected Copper Wire Resistance row carried into 2 calculator workflows.
- Next
- Choose the matching row, review selection checks, then open the calculator or worksheet that consumes the value.
Source governance
Record how this table is used before carrying a value into a calculator, worksheet, or authority workflow.
| Governance item | Record | Use boundary |
|---|---|---|
| Source class | Electrical property lookup | Use the table as a controlled reference input, not as an adoption or approval database. |
| Last review basis | Static registry review | Re-check adopted standards, manufacturer data, and project criteria before final use. |
| Known limit | Temperature, insulation, listing, and circuit conditions can change final conductor selection. | Escalate unresolved code, listing, or jurisdiction questions to the project record. |
| Downstream record | Fire Alarm NAC Voltage Drop Calculator, Fire Alarm Wire Resistance Calculator, Fire Alarm Battery and NAC Worksheet | Keep selected rows with the worksheet, calculation package, or authority record. |
Reference table structure
Use these fields to filter the table, select a value, and retain the basis with the calculation record.
Rows
6
Filter fields
Wire Size
Value columns
Ohms per 1000 ft
Related pages
3
| Table area | Values | Engineering use |
|---|---|---|
| Query examples | Wire Size = 12 AWG; Wire Size = 14 AWG; Wire Size = 16 AWG | Use these values as table filters before carrying a row into a calculator. |
| Related calculators | Fire Alarm NAC Voltage Drop Calculator, Fire Alarm Wire Resistance Calculator | Selected rows become calculation inputs or reasonableness checks for the linked tools. |
| Related worksheets | Fire Alarm Battery and NAC Worksheet | Worksheet records preserve the selected value with the project assumption trail. |
Reference table use
Use the table as controlled input data: select the row, verify the condition, and carry the value to the related calculator.
Usage context
- 1Use this table when fire alarm voltage drop or circuit resistance needs conductor resistance by AWG size.
- 2Carry ohms per 1000 ft into round-trip circuit calculations using one-way route length and the selected conductor size.
- 3Keep the conductor row with battery, NAC, and voltage-drop records when circuit acceptance depends on end-of-line voltage.
Selection rules
- 1Match AWG size and conductor material basis before using ohms per 1000 ft.
- 2Use one-way route length in calculators that explicitly compute round-trip resistance.
- 3Do not substitute wire size to pass voltage drop without confirming listing, installation, and project requirements.
Review checks
- 1Wire size and resistance row match the circuit conductor used in drawings or field review.
- 2Round-trip resistance is computed from the correct one-way route length.
- 3End-of-line voltage, NAC load, and battery records use compatible source voltage and device current assumptions.
| Reference field | How to use it | Related tools |
|---|---|---|
| Wire Size | Use this field to identify the matching project condition. | Fire Alarm NAC Voltage Drop Calculator, Fire Alarm Wire Resistance Calculator, Fire Alarm Battery and NAC Worksheet |
| Ohms per 1000 ft | Carry this value into the downstream calculator with the displayed units and label. | Fire Alarm NAC Voltage Drop Calculator, Fire Alarm Wire Resistance Calculator, Fire Alarm Battery and NAC Worksheet |
Selection examples
Use these examples to choose a row deliberately before carrying the value into a calculator or worksheet.
| Scenario | Row choice | Reason | Downstream use |
|---|---|---|---|
| A NAC voltage drop check uses 14 AWG copper conductors. | Select the 14 AWG resistance row for the conductor basis used on the drawing. | Voltage drop depends on conductor resistance, circuit current, and round-trip length. | Carry ohms per 1000 ft into the voltage-drop calculator with one-way route length and circuit current. |
| The circuit is too close to the listed appliance minimum voltage. | Compare a larger AWG row only if the installation and project documents can support the conductor change. | Wire size is a design and installation decision, not a value to swap silently for a pass result. | Update NAC load, voltage drop, and battery/NAC worksheet records if conductor size changes. |
| Field notes give cable route length but not whether it is one-way or loop length. | Pause row use until route length basis is confirmed. | Applying round-trip resistance to an already doubled length can overstate voltage drop. | Document one-way route length before computing end-of-line voltage. |
Using AWG resistance for NAC voltage drop
Assumptions
- 1A notification appliance circuit uses 14 AWG copper conductors.
- 2The one-way route length is 300 ft and circuit current is known from listed appliance data.
- 3The voltage-drop calculator applies round-trip conductor length.
Steps
- 1Select the 14 AWG resistance row and keep units as ohms per 1000 ft.
- 2Enter one-way route length into the voltage-drop calculator so round-trip resistance is applied once.
- 3Use listed appliance current for the selected candela or device setting.
- 4Compare end-of-line voltage against the listed appliance operating range.
Result
The workpaper ties conductor size, round-trip resistance, circuit current, and voltage drop together so a reviewer can see why the end-of-line voltage passed or failed.
Misuse warnings
- 1Do not apply round-trip resistance twice by entering a doubled route length into a calculator that already doubles one-way length.
- 2Do not switch AWG size only to pass voltage drop without updating drawings, installation basis, and worksheet records.
- 3Do not use resistance values without confirming conductor material and listed circuit assumptions.
Copper Wire Resistance
| Wire Size | Ohms per 1000 ft |
|---|---|
| 12 AWG | 1.588 |
| 14 AWG | 2.525 |
| 16 AWG | 4.016 |
| 18 AWG | 6.385 |
| 20 AWG | 10.15 |
| 22 AWG | 16.14 |
Engineering disclaimer
NFPA in USA provides engineering workpapers, calculation checks, and reference tables for project screening and coordination. Final design decisions, code interpretations, submittals, and acceptance records must be completed by qualified professionals and verified against the adopted code, project criteria, listings, and Authority Having Jurisdiction requirements. This site does not issue signed or sealed engineering documents.Tools and workflows that use this table
FAQ
How should this wire resistance table be used?+
Use it as an engineering reference source for selecting values, checking assumptions, and documenting the basis carried into a calculator or worksheet.
Can this table replace the sealed project record?+
No. Values still need to be checked against the adopted standard, manufacturer data, project specifications, and Authority Having Jurisdiction requirements before they are used in final documents.