Ohm is the SI unit of electrical resistance.
Ohms to Rontoohms Converter — Ohm to rOhm
Convert Ohm (Ohm) to Rontoohm (rOhm) using the exact conversion factor (1 ohm = 1e+27 rontoohm). See the formula, worked examples, conversion table, history, and common uses.
Ohms to Rontoohms converter
Converter
Electricity Converter
Convert electrical units by family and calculate voltage, current, resistance, power, and energy with context values.
Context values
Some unit families need one extra value for a physically accurate result.
Rontoohm is 1e-27 ohm units.
Result = input x 1 / 1e-27.
Electrical units in the same family convert directly.
Reserved above the conversion cards and below the converter.
About Converting Ohms to Rontoohms
Ohm and Rontoohm both belong to the electricity family — voltage, current, resistance, power, or energy — units that show up constantly when working across the different standards used by household wiring (120V/240V depending on region), automotive electrical systems (12V/24V), and electronics design. Ohm is most often used for resistor and circuit-component ratings.
Formula
rontoohms = ohms × 1e+27
This factor comes from each unit's defined relationship to the category's base unit: 1 ohm equals 1 base unit, and 1 rontoohm equals 1e-27 base units, so dividing one by the other gives the direct ohm-to-rontoohm factor of 1e+27.
Simple example
1 Ohm × 1e+27 = 1e+27 rOhm
1 ohm = 1e+27 rontoohms.
Real-world example
120 Ohm × 1e+27 = 1.2e+29 rOhm
120 ohms = 1.2e+29 rontoohms.
Conversion table
| Ohm (Ohm) | Rontoohm (rOhm) |
|---|---|
| 1 Ohm | 1e+27 rOhm |
| 5 Ohm | 5e+27 rOhm |
| 12 Ohm | 1.2e+28 rOhm |
| 24 Ohm | 2.4e+28 rOhm |
| 120 Ohm | 1.2e+29 rOhm |
| 240 Ohm | 2.4e+29 rOhm |
Reverse conversion: Rontoohm to Ohm
1e+27 rOhm × 1e-27 = 1 Ohm
1e+27 rontoohms = 1 ohm.
ohms = rontoohms × 1e-27
For a page dedicated to this direction, see Rontoohm to Ohm.
Understanding the Ohm
Ohm (Ohm) measures electrical resistance. The SI derived unit of electrical resistance, equal to one volt per ampere. It is classified as a SI derived unit.
Where it's used: Universal — SI derived unit used worldwide
Uses of the Ohm today
- Resistor and circuit-component ratings
- Electrical wiring and grounding specifications
- Audio equipment impedance ratings
History of the Ohm
The ohm is named after Georg Simon Ohm (1789–1854), a German physicist who published Ohm's law in 1827, describing the relationship between voltage, current, and resistance (V = I × R) — the relationship the unit itself is defined through.
Historical origin. Ohm was not the invention of a single named person; it developed through the process described above.
Understanding the Rontoohm (rOhm)
Rontoohm is 1e-27 ohm units.
Ohm — sources
- BIPM SI Brochure, 9th edition — Definition of the ohm as a coherent SI derived unit.
Reserved between the cards and the FAQ so the page stays balanced.
Frequently asked questions
How many rontoohms are in 1 ohm?
1 ohm equals 1e+27 rontoohms, using the exact defined conversion factor rather than an estimate.
How do I convert ohm to rontoohm?
Multiply the ohm value by 1e+27. The converter above does this instantly to whatever precision you set.
How do I convert rontoohm back to ohm?
Use the reverse factor: 1 rontoohm equals 1e-27 ohms. You can also use the swap control in the converter above to flip the direction instantly.
What is a ohm?
Ohm (Ohm) measures electrical resistance. The SI derived unit of electrical resistance, equal to one volt per ampere. It is classified as a SI derived unit.
What is a rontoohm?
Rontoohm (rOhm) is a unit of electricity.
Is the ohm to rontoohm conversion exact?
Yes. Both ohm and rontoohm are defined by fixed standards rather than physical artifacts, so the factor of 1e+27 used above is exact to as many digits as you choose to display.
Where is the ohm still used today?
Universal — SI derived unit used worldwide
What's the difference between voltage, current, and resistance?
Voltage (volts) is the electrical potential difference driving current through a circuit. Current (amperes) is the rate of flow of electric charge. Resistance (ohms) is how much a component opposes that flow. They're related by Ohm's law (V = I × R), but they are distinct physical quantities, and this page converts between units of just one of them.