Overview
Some unit conversions come up constantly — metres to feet, Celsius to Fahrenheit — and are covered by simple, well-known converters. Others are less common but still essential in specific fields: converting a CGS-era physics textbook value to SI, translating a materials hardness spec between Rockwell and Vickers, or converting a decimal-degree GPS coordinate to the degrees-minutes-seconds format an old survey document uses. This guide collects those less common but genuinely useful conversions in one place.
Several of these conversions rely on standard approximations rather than exact physical constants — that's noted explicitly for each one below, since it matters for how much precision you can expect from the result.
Step 1: Convert Between CGS and SI Units
Physics problems, older research papers, and electromagnetism in particular still use CGS (centimetre-gram-second) units like the dyne, erg, and gauss alongside modern SI units like the newton, joule, and tesla. The CGS to SI Units Converter covers force, energy, pressure, viscosity, and magnetic flux density conversions between the two systems, each using an exact conversion factor.
Step 2: Convert Material Hardness Scales
Material spec sheets and quality reports don't always agree on which hardness scale to use — a part might be specified in Rockwell C while a supplier's certificate reports Brinell. Because different hardness tests use different indenter shapes and loads, there's no single formula connecting them; instead, the Hardness Scale Converter interpolates against a standard steel-based correlation table (closely following ASTM E140) to estimate the equivalent value in Rockwell, Brinell, Vickers, Shore D, or Mohs.
Step 3: Convert Concentration Units
Water quality reports, lab results, and chemistry problems use a range of concentration units — percent, ppm, ppb, and mg/L among them — and comparing a result against a regulatory threshold often requires converting between them. The Concentration Converter handles this using the standard dilute-solution approximation (1 mg/L ≈ 1 ppm for water-based solutions), which covers the vast majority of environmental and lab reporting contexts.
Step 4: Convert Radiation Dose Units
Medical imaging reports and occupational radiation safety logs use sievert and millisievert internationally, but the US commonly uses the older rem and millirem instead — a factor-of-100 difference at every level that's easy to get wrong manually. The Radiation Dose Converter converts between sievert, gray, rad, and rem, treating gray and sievert (and rad and rem) as numerically equivalent for the X-ray, gamma, and beta radiation types involved in most medical and occupational contexts.
Step 5: Convert GPS Coordinates Between Formats
A survey document, nautical chart, or historical map might list a coordinate in degrees-minutes-seconds (DMS) format, while your GPS device or mapping app expects decimal degrees, or vice versa. The Coordinates Converter keeps both formats in sync for latitude and longitude simultaneously, so editing either representation updates the other instantly.
Step 6: Convert Sieve Mesh Size to Micron Particle Size
Sieve and filtration specifications are typically labelled by mesh number (openings per linear inch), while particle size data from lab instruments is usually given in microns — and because mesh number and opening size are inversely related, converting between them isn't a simple multiplication. The Mesh-to-Micron Converter applies the standard industry approximation used across sieve manufacturers (microns ≈ 15,000 ÷ mesh).
Key Terms
- CGS System — the centimetre-gram-second unit system, predating SI, still used in some physics and electromagnetism contexts
- Vickers Hardness (HV) — a hardness scale using a diamond pyramid indenter, commonly used as the reference scale for converting between other hardness scales
- ppm — parts per million; a ratio-based concentration unit, approximately equal to mg/L in dilute water-based solutions
- Sievert (Sv) — the SI unit of equivalent radiation dose, weighted by how biologically damaging the radiation type is
- DMS — Degrees, Minutes, Seconds; a traditional coordinate notation still used in surveying, aviation, and nautical navigation