How to Read a 4 Digit SMD Resistor?

Reading a 4-digit SMD resistor code is straightforward: the first three digits represent the significant figures, and the fourth digit is the multiplier.

Understanding the 4-Digit SMD Resistor Code

Unlike the 3-digit code, the 4-digit format provides greater precision for surface-mount device (SMD) resistors. The code is typically printed directly on the small component.

Based on the Resistor Code Format reference:

• The beginning values (the first three digits) are used to indicate the significant digits of the resistance value.
• The last digit (the fourth digit) is the multiplier. This digit tells you how many zeros to add after the significant digits.
• The character 'R' is used to indicate the position of a decimal point.

This four-digit format inherently allows for higher precision compared to the common 3-digit codes.

How to Decode the Value

Here's how to break down the code:

1. Identify the first three digits. These are your base number.
2. Identify the fourth digit. This is the power of ten you multiply the base number by. The number represents the exponent for 10 (i.e., if the fourth digit is 3, the multiplier is 10³ = 1000).
3. If the code includes 'R', the digits before the 'R' are the whole number part, and the digits after the 'R' are the fractional part. 'R' effectively acts as a decimal point.

Examples of 4-Digit Codes

Let's look at a few examples to illustrate:

SMD Code	Significant Digits	Multiplier Digit	Multiplier (10^n)	Calculation	Resistance Value
1001	100	1	10¹ (10)	100 * 10	1000 Ohms (1kΩ)
4702	470	2	10² (100)	470 * 100	47000 Ohms (47kΩ)
2203	220	3	10³ (1000)	220 * 1000	220000 Ohms (220kΩ)
33R4	33R4 (R is decimal)	N/A	N/A	33.4	33.4 Ohms
R500	R500 (R is decimal)	N/A	N/A	0.500	0.5 Ohms

In the examples using 'R', the 'R' replaces the decimal point. So, 33R4 is read as 33.4 Ohms, and R500 is read as 0.500 Ohms.

By following these simple steps, you can accurately determine the resistance value of a 4-digit SMD resistor.