Touch Voltage / Body Current
V = I × R_body
Quick answer
This calculator solves V_touch = I_body × R_body for Touch Voltage. With Body Resistance 0.47 kΩ, Body Current 20 mA, the result is 9.4 V. It solves in 3 directions, so you can enter the values you have and get the one you need.
Calculator
Formula
Description
Touch voltage safety analysis uses Ohm's law to determine the current flowing through a person who contacts an energized surface. The IEC 61140 standard limits touch voltage to 50V AC RMS or 120V DC in normal conditions. Human body resistance varies widely depending on skin moisture, contact area, and voltage level, but 1000Ω is commonly used as a conservative estimate for wet conditions (IEC 60479-1). At 50V across 1000Ω body resistance, the current is 50 mA, which is at the threshold of ventricular fibrillation.
Variables
- V — Touch voltage (V)
- R — Human body resistance (Ω)
- I — Current flowing through the body (A)
Practical Notes
IEC 60479-1 body impedance ranges: dry conditions ~2000-5000Ω hand-to-hand, wet conditions ~500-1000Ω. Currents above 10 mA cause involuntary muscle contraction (cannot let go), above 30 mA risk respiratory arrest, and above 75 mA risk ventricular fibrillation. Equipment Class I (grounded) and Class II (double insulated) protection schemes are designed to keep touch voltage below safe limits.
Symbols and units
| Symbol | Meaning | Default unit | Accepted units |
|---|---|---|---|
| V | Touch Voltage | V | pV, nV, µV, mV, V, kV |
| R | Body Resistance | Ω | mΩ, Ω, kΩ, MΩ |
| I | Body Current | mA | pA, nA, µA, mA, A, kA |
Step by step
- 1. What you know: Body Resistance 0.47 kΩ, Body Current 20 mA
- 2. The relation: V_touch = I_body × R_body
- 3. Substitute: R = 0.47 kΩ, I = 20 mA
- 4. Result: Touch Voltage = 9.4 V
Related quantities from the same inputs
- P = V × I = 0.188 W
Worked examples
Minimum range
Given: Body Resistance 1 Ω, Body Current 100 µA
Result: Touch Voltage = 100 µV
Low range
Given: Body Resistance 10 Ω, Body Current 1 mA
Result: Touch Voltage = 10 mV
Typical
Given: Body Resistance 0.47 kΩ, Body Current 20 mA
Result: Touch Voltage = 9.4 V
High range
Given: Body Resistance 4.7 kΩ, Body Current 0.5 A
Result: Touch Voltage = 2.35 kV
Maximum range
Given: Body Resistance 47 kΩ, Body Current 5 A
Result: Touch Voltage = 235 kV
Solving for each variable
Solve for Touch Voltage
Body Resistance 1 Ω, Body Current 100 µA → 100 µV
Solve for Body Resistance
Touch Voltage 0.33 V, Body Current 100 µA → 3.3 kΩ
Solve for Body Current
Touch Voltage 0.33 V, Body Resistance 1 Ω → 0.33 A
How Touch Voltage changes with Body Resistance
| Body Resistance (input) | Touch Voltage (result) |
|---|---|
| 47 Ω | 0.94 V |
| 117.5 Ω | 2.35 V |
| 0.235 kΩ | 4.7 V |
| 0.3525 kΩ | 7.05 V |
| 0.47 kΩ | 9.4 V |
| 0.705 kΩ | 14.1 V |
| 0.94 kΩ | 18.8 V |
| 1.88 kΩ | 37.6 V |
| 3.29 kΩ | 65.8 V |
| 4.7 kΩ | 94 V |
The same result in other units
| Unit | Value |
|---|---|
| µV | 9400000 |
| mV | 9400 |
| V | 9.4 |
| kV | 0.0094 |
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<p><a href="https://vbatpower.com/formulas/touch-voltage-limit/">Touch Voltage / Body Current</a> Calculator by vbatpower.com</p>Frequently asked questions
How do you calculate Touch Voltage / Body Current?
Use V_touch = I_body × R_body. With Body Resistance 0.47 kΩ, Body Current 20 mA, Touch Voltage works out to 9.4 V.
What is the formula for Touch Voltage / Body Current?
The formula is V_touch = I_body × R_body. Touch voltage safety analysis uses Ohm's law to determine the current flowing through a person who contacts an energized surface.
How do you find Body Resistance when you know the other values?
Rearrange for Body Resistance: with Touch Voltage 0.33 V, Body Current 100 µA, Body Resistance is 3.3 kΩ.
How do you find Body Current when you know the other values?
Rearrange for Body Current: with Touch Voltage 0.33 V, Body Resistance 1 Ω, Body Current is 0.33 A.
What units does Touch Voltage / Body Current use?
Touch Voltage is shown in µV, mV, V, kV. Values are held in SI base units internally, so you can mix prefixes without converting by hand.
Related Concepts
All Safety / Protection formulas →Need more features?
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