CGS System of Units Converter
Convert common mechanical and Gaussian CGS quantities to and from SI with one consistent, unit-aware model.
Conversion inputs
Live result
Conversion reference
| Quantity | SI unit | CGS unit | 1 CGS unit in SI |
|---|
Electromagnetic entries use the Gaussian CGS convention. Because electromagnetic quantity definitions differ among CGS subsystems, do not apply these factors to ESU or EMU data without checking the convention used by the source.
How to use the CGS System of Units Converter
What this calculator does. This tool converts one numerical value between the International System of Units and a corresponding unit in the centimetre – gram – second system. It covers six common mechanical quantities and four Gaussian electromagnetic quantities. The result is an exact unit conversion based on the stated factor; it does not determine the physical quantity from an experiment, estimate uncertainty, or decide which electromagnetic CGS subsystem an old paper intended.
When to use it. Use the converter when checking a physics textbook that reports force in dynes, translating laboratory energy data from ergs to joules, converting viscosity values from poise or stokes into SI, or interpreting Gaussian magnetic and electrical quantities in theoretical-physics or astrophysics material. For formal reporting, consult the NIST guidance on unit conversion and rounding and retain enough significant digits for the measurement.
How to calculate. The calculator opens with a demonstration of standard gravitational acceleration: 9.80665 m/s², which is 980.665 Gal. A validated example workbook is immediately available.
- Select a Physical quantity. The unit labels and factor update immediately.
- Replace either the SI value or the CGS value. The last field you edit becomes the source, and the other field is recalculated live.
- Read the primary equivalent, the paired SI and CGS values, the CGS-to-SI factor, and the conversion direction. The reference table provides a compact cross-check.
- Select Download Excel to export the current typed inputs and results as a validated OOXML workbook. Reset clears the demonstration values and results; export remains unavailable until a complete valid value is entered again.
Input guide. Physical quantity is required and uses a fixed list; choose the quantity actually represented by your source data, because equal-looking numbers for energy and pressure have different dimensions. SI value is an optional source field whenever the CGS field is present, and vice versa; at least one must contain a valid finite decimal. Accepted input uses a period as the decimal separator, optional sign, and optional scientific notation such as 1.2e-5. Commas and embedded unit symbols are rejected to prevent ambiguous interpretation. Negative values are allowed because signed vector components and potential differences can be meaningful. A realistic SI example is 1.25 N; changing it produces 125,000 dyn. A realistic CGS example is 250 erg; changing it produces 0.000025 J. Do not paste “1,5”, “10 dyn”, or a value copied with a Unicode multiplication sign; enter only the number.
Output guide. CGS equivalent or SI equivalent is the primary result, depending on which field was edited last. SI value and CGS value show the same physical quantity in both systems. CGS-to-SI factor means one CGS unit multiplied by that factor equals the SI value; therefore SI = CGS × factor and CGS = SI ÷ factor. Conversion direction documents which input drove the latest calculation. Zero converts exactly to zero, negative values retain their sign, and very large or small values may display in scientific notation. These outputs are identities under the selected convention, not recommendations.
Worked example. For acceleration, 1 Gal equals 0.01 m/s². Starting with 9.80665 m/s², divide by 0.01: 9.80665 ÷ 0.01 = 980.665 Gal. The startup result, table factor, live summary, and workbook all use those same values. This is also equivalent to 980.665 cm/s² because the gal is defined as one centimetre per second squared.
Learn more. The NIST Guide to SI conversion factors explains how conversion factors are selected and applied, while the BIPM SI Brochure defines the modern SI framework used for the SI side of every conversion.
How the factors work
Mechanical CGS conversions follow directly from the centimetre, gram, and second base units. One dyne is 10 – 5 newtons, one erg is 10 – 7 joules, one barye is 0.1 pascal, one poise is 0.1 pascal-second, and one stokes is 10 – 4 square metres per second. Because these factors are powers of ten, the conversion itself introduces no approximation; only the precision of the entered measurement and displayed rounding limit the reported result.
CGS value = SI value ÷ factor
Gaussian electromagnetic units need more care. Their equations and quantity definitions do not map to SI in the same purely mechanical way. This converter uses explicit numerical factors for franklin, statvolt, gauss, and oersted and labels them as Gaussian. The NIST reference on SI units is useful when preparing modern technical work, where SI is generally preferred.
Common mistakes
- Choosing a unit with the same symbol but a different meaning, such as P for poise versus a variable named P for power.
- Treating “CGS” as a single electromagnetic convention. Gaussian, ESU, and EMU expressions can differ.
- Rounding the conversion factor before multiplying. Keep the canonical factor and round only the final presentation.
- Confusing gauss with the reference page's historical shorthand. This converter uses the standard relation 1 G = 10 – 4 T.