R notation is used in the supported SMD decoder for printed marks where the letter R takes the place of a decimal point. This page focuses on one job: reading 4R7, R22, R010, and 0R22 without dropping the R or treating it as a multiplier. Enter the complete printed mark in the SMD Resistor Code Decoder, then verify the part family and specification in the product series datasheet.
R is the decimal position
When R appears in these supported markings, read it as the location of the decimal point. The characters before and after R remain part of the numeric value. This is different from the three-digit and four-digit rules, where the final digit supplies a multiplier. The safest input is the exact printed text, including a leading zero when one is present.
Read 4R7
4R7 reads as 4.7 ohms. The R sits between the whole-number digit and the fractional digit, so the mark is not 47 ohms and not a three-digit code. The calculator uses the R position to return the resistance result and the code-system detail.
Read R22
R22 reads as 0.22 ohms in the supported rule. A leading R places the decimal point before the following digits. Do not delete the R and enter 22, because that changes the value and loses the information carried by the printed marking.
Read R010 and 0R22
| Printed mark | R position | Decoded result |
|---|---|---|
| R010 | Before 010 | 0.010 ohm |
| 0R22 | After the leading 0 | 0.22 ohm |
Both marks use R as a decimal separator, but the surrounding digits are different. R010 preserves three digits after the decimal position, while 0R22 prints a leading zero before R. Read the entire mark rather than normalizing it by eye into a different code.
Low-ohm markings need more evidence
R notation can identify a nominal resistance candidate, but it does not describe the part's power, voltage, current, pulse, temperature, construction, or layout requirements. Those details are especially important for low-ohm parts. Use the code as one piece of printed-marking evidence and return to the product series datasheet before selecting a replacement or making a circuit decision.
Do not mix code systems
A visible R is a reason to use this guide, not to force the mark into the three-digit or four-digit rule. If the printed characters are uncertain, keep the literal alternatives visible and compare the package, manufacturer, board reference, and product series documentation. The 3-Digit SMD guide and 4-Digit SMD guide cover numeric marks without R; the Zero-Ohm guide covers the documented zero-ohm helper markings.
Source and limits
This page is limited to the supported R-decimal printed SMD marking rule and the examples 4R7, R22, R010, and 0R22. It explains how to read the code position; it does not establish the complete electrical specification of a component.
- Use the SMD Resistor Code Decoder, then check tolerance, specification, package, and manufacturer series in the product series datasheet.
- Do not replace R with a guessed multiplier, and do not treat an SMD printed mark as a through-hole color-band code.
- Keep uncertain readings as candidates and do not use a code-only result for safety, procurement, compliance, or replacement decisions.