The Lab Unit Conversions That Actually Cause Errors
Most unit conversions are second nature after enough practice — but a handful genuinely trip people up, usually because they look similar to something else or because a protocol was written using a different convention than the one you're used to.
Conversions worth double-checking
| Mix-up | Why it happens |
|---|---|
| µg vs mg vs g | Handwritten "µ" can look like "m" in old notebooks or unclear scans |
| µL vs mL | Same visual confusion, and a 1000x error that's easy to miss when a volume "looks reasonable" either way |
| rpm vs g-force (RCF) | Centrifuge speed protocols sometimes specify one, sometimes the other — they aren't interchangeable without knowing the rotor radius |
| °C vs K | Most lab work uses Celsius, but some equations (ideal gas law, Arrhenius) require Kelvin |
| psi vs bar vs atm | Pressure units vary by equipment manufacturer and country of origin |
RPM to RCF — the one that actually needs a formula, not a lookup
Unlike most conversions, RPM and relative centrifugal force (RCF, in units of × g) aren't a fixed ratio — the relationship depends on your specific rotor's radius:
This is why a protocol written for one centrifuge's rotor can give a meaningfully different actual force on a different machine, even at the "same" RPM — always check whether a protocol specifies RPM or RCF, and use your own rotor's radius when converting.
💡 When copying an old protocol
If you're following a protocol written years ago, or from a different lab, double-check unit conventions explicitly — older or international protocols sometimes use unit conventions (e.g., × g force written simply as a number, without units, next to an RPM value) that are easy to misread out of context.
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