Convert measured wire resistance to one-way distance or predict resistance from length using AWG or custom area, copper or aluminum, temperature, loop length, and voltage-drop checks.

Estimate for a uniform conductor with known area and material. A loop assumes two identical conductors. Lead/contact resistance and cable construction can bias distance; this is not an ampacity or fault-location check.

20°C is the reference assumption. Linear correction is limited to −20°C through100°C.

Optional settings

Blank omits voltage drop and power loss.

Ohms To Distance Formula

Resistance (Ω) is not resistivity (Ω·m). For a uniform single conductor, the following formula estimates conductor length from measured resistance, metal cross-sectional area and resistivity at the conductor temperature.

D = (R × A) / ρ

Variables:

  • D is the one-conductor length (meters)
  • R is the resistance (ohms)
  • A is the cross-sectional area of the material (square meters)
  • ρ is the resistivity of the material (ohm meters)

For one conductor, multiply resistance by metal area and divide by resistivity. For a measured supply-and-return loop of two identical conductors, divide that result by two to obtain one-way distance. Lead/contact resistance, unknown alloy, strand lay or temperature variation can bias the estimate. The calculator uses approximate material constants and a linear temperature model limited to −20…100°C.

Ohms to Distance Conversion Table (Copper, A = 1.00 mm², ρ = 1.72×10⁻⁸ Ω⋅m @ 20°C)
Resistance (Ω) Distance (m) Distance (ft)
0.052.9079.543
0.15.81419.087
0.211.62838.173
0.317.44257.260
0.529.07095.433
0.7543.605143.150
158.140190.866
1.587.209286.299
2116.279381.732
3174.419572.598
4232.558763.465
5290.698954.331
7.5436.0471431.496
10581.3951908.661
12697.6742290.394
15872.0932862.992
201162.7913817.323
251453.4884771.654
301744.1865725.984
502906.9779543.307
Assumes copper at 20°C with cross-sectional area A = 1.00 mm² (1×10⁻⁶ m²) and resistivity ρ = 1.72×10⁻⁸ Ω⋅m. Formula: L = (R × A) / ρ. Results scale linearly with A and inversely with ρ.

How to Calculate Ohms To Distance?

The following steps outline how to calculate the Ohms To Distance.

  1. First, determine the resistance (R) in ohms.
  2. Next, determine the cross-sectional area (A) of the material in square meters.
  3. Next, determine the resistivity (ρ) of the material in ohm meters.
  4. Next, gather the formula from above = D = (R * A) / ρ.
  5. Finally, calculate the Ohms To Distance (D).
  6. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

Resistance (R) = 1 ohm, measured on one conductor at20°C

Metal cross-sectional area (A) = 1 mm² = 1 ×10⁻⁶ m²

Assumed copper resistivity (ρ) = 1.724 ×10⁻⁸ Ω·m. Then D = 1 ×10⁻⁶ / (1.724 ×10⁻⁸) ≈ 58.0046 m. The table above uses its explicitly stated rounded value1.72 ×10⁻⁸, so its results differ slightly. This estimate does not establish cable ampacity.