Siemens is the SI unit of conductance.
Siemens to Femtosiemens Converter — S to fS
Convert Siemens (S) to Femtosiemens (fS) using the exact conversion factor (1 siemens = 1e+15 femtosiemens). See the formula, worked examples, and conversion table.
Siemens to Femtosiemens 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.
Femtosiemens is 1e-15 siemens units.
Result = input x 1 / 1e-15.
Electrical units in the same family convert directly.
Reserved above the conversion cards and below the converter.
About Converting Siemens to Femtosiemens
Siemens and Femtosiemens 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. Specifically: Siemens is the SI unit of conductance, and femtosiemens is 1e-15 siemens units.
Formula
femtosiemens = siemens × 1e+15
This factor comes from each unit's defined relationship to the category's base unit: 1 siemens equals 1 base unit, and 1 femtosiemens equals 1e-15 base units, so dividing one by the other gives the direct siemens-to-femtosiemens factor of 1e+15.
Simple example
1 S × 1e+15 = 1e+15 fS
1 siemens = 1e+15 femtosiemens.
Real-world example
120 S × 1e+15 = 1.2e+17 fS
120 siemens = 1.2e+17 femtosiemens.
Conversion table
| Siemens (S) | Femtosiemens (fS) |
|---|---|
| 1 S | 1e+15 fS |
| 5 S | 5e+15 fS |
| 12 S | 1.2e+16 fS |
| 24 S | 2.4e+16 fS |
| 120 S | 1.2e+17 fS |
| 240 S | 2.4e+17 fS |
Reverse conversion: Femtosiemens to Siemens
1e+15 fS × 1e-15 = 1 S
1e+15 femtosiemens = 1 siemens.
siemens = femtosiemens × 1e-15
For a page dedicated to this direction, see Femtosiemens to Siemens.
Understanding the Siemens (S)
Siemens is the SI unit of conductance.
Understanding the Femtosiemens (fS)
Femtosiemens is 1e-15 siemens units.
Reserved between the cards and the FAQ so the page stays balanced.
Frequently asked questions
How many femtosiemens are in 1 siemens?
1 siemens equals 1e+15 femtosiemens, using the exact defined conversion factor rather than an estimate.
How do I convert siemens to femtosiemens?
Multiply the siemens value by 1e+15. The converter above does this instantly to whatever precision you set.
How do I convert femtosiemens back to siemens?
Use the reverse factor: 1 femtosiemens equals 1e-15 siemens. You can also use the swap control in the converter above to flip the direction instantly.
What is a siemens?
Siemens (S) is a unit of electricity.
What is a femtosiemens?
Femtosiemens (fS) is a unit of electricity.
Is the siemens to femtosiemens conversion exact?
Yes. Both siemens and femtosiemens are defined by fixed standards rather than physical artifacts, so the factor of 1e+15 used above is exact to as many digits as you choose to display.
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.