# Surface Mount Resistor Guide: Sizes, Codes, Types & Values

_Published: 2026-09-09_

Table of Contents

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- What Is a Surface Mount Resistor?
- What Are the Main Surface Mount Resistor Types?
- What Surface Mount Resistor Sizes Are Common?
- How Do You Read Surface Mount Resistor Codes and Markings?
- Surface Mount Resistor Values: What Do 100, 101, 102 and 103 Mean?
- How Do You Choose the Right Surface Mount Resistor for a PCB?
- Surface Mount Resistor vs Through-Hole Resistor: Which Should You Use?
- FAQs About Surface Mount Resistors

[A surface mount resistor](https://www.bestpcbs.com/blog/2026/09/surface-mount-resistor/) is a compact resistor mounted directly onto PCB pads and assembled using surface mount technology. Common packages range from tiny 01005 and 0201 parts to larger 1206, 2010, and 2512 resistors used where more power or board space is available.

Selecting the right part involves more than resistance value. Engineers also need to consider resistor type, package size, tolerance, power rating, working voltage, TCR, and markings. This guide explains the most common surface mount resistor sizes, types, codes, and values, then shows how to choose one for a PCB.

![Surface mount resistor mounted on a printed circuit board](https://www.bestpcbs.com/blog/wp-content/uploads/2026/09/surface-mount-resistor-hero.jpg)

## What Is a Surface Mount Resistor?

A surface mount resistor is a resistor designed to sit directly on conductive pads on the surface of a PCB. It does not use long leads passing through drilled holes like a through-hole resistor.

Other names commonly used for the same component include:

- SMD resistor
- chip resistor
- surface mount chip resistor
- SMT resistor

SMD means surface-mount device, while SMT refers to the process used to assemble surface-mount components.

A typical chip resistor contains:

- a ceramic substrate
- a resistive layer
- metal terminal electrodes
- a protective coating

During [PCB assembly](https://www.bestpcbs.com/blog/2026/09/automated-pcb-assembly/), solder paste is printed on the pads, the resistor is placed by pick-and-place equipment, and the joint is formed during reflow soldering.

The surface mount resistor symbol on a schematic is normally the same standard resistor symbol used for a through-hole part. Its reference designator is usually `R`, such as R1 or R24. Package information such as 0603 or 0805 is defined in the PCB footprint rather than the schematic symbol.

## What Are the Main Surface Mount Resistor Types?

The main surface mount resistor types differ in resistive material, precision, temperature stability, current capability, and cost.

![Comparison of thick film, thin film, metal strip, metal foil, wirewound and fusible surface mount resistor types](https://www.bestpcbs.com/blog/wp-content/uploads/2026/09/surface-mount-resistor-types.jpg)

Type
Main Characteristic
Common Use

Thick film
Cost-effective and widely available
General PCB circuits

Thin film
High precision and low TCR
Analog and measurement circuits

Metal strip
Very low resistance
Current sensing

Metal foil
High stability and accuracy
Precision electronics

SMD wirewound
Higher power and pulse capability
Power circuits

Fusible
Designed to open under overload
Circuit protection

**Thick-film resistors**

These are the standard choice for many PCB designs. They cover a broad resistance range and are readily available in packages such as 0402, 0603, 0805, and 1206.

Typical uses include:

- pull-up and pull-down networks
- LED current limiting
- bias circuits
- general signal conditioning

**Thin-film resistors**

Thin-film parts are used when tighter tolerance and lower temperature coefficient are required. They are common in:

- precision amplifiers
- sensor interfaces
- measurement circuits
- accurate voltage dividers

**Metal strip resistors**

Metal strip parts are mainly used for low-resistance current sensing. Values may be measured in milliohms rather than ohms, making them useful in battery systems, power supplies, motor drives, and power converters.

The resistor type should therefore match the electrical requirement. Two resistors with the same resistance and package size can have very different tolerance, TCR, pulse capability, and stability.

## What Surface Mount Resistor Sizes Are Common?

Common surface mount resistor sizes include 0201, 0402, 0603, 0805, 1206, 2010, and 2512. Smaller packages reduce PCB area, while larger packages generally offer higher power capability and easier handling.

![Surface mount resistor size comparison from 0201 to 2512 packages](https://www.bestpcbs.com/blog/wp-content/uploads/2026/09/surface-mount-resistor-sizes.jpg)

Imperial Size
Metric Code
Approx. Size (mm)
Typical Conventional Power*

01005
0402
0.4 × 0.2
~0.03 W

0201
0603
0.6 × 0.3
~0.05 W

0402
1005
1.0 × 0.5
~0.063 W

0603
1608
1.6 × 0.8
~0.10 W

0805
2012
2.0 × 1.25
~0.125 W

1206
3216
3.2 × 1.6
~0.25 W

1210
3225
3.2 × 2.5
~0.5 W

2010
5025
5.0 × 2.5
~0.75 W

2512
6332
6.3 × 3.2
~1 W

*These are common reference ratings rather than universal specifications. The exact rating must be checked in the resistor manufacturer’s datasheet.

The imperial package code approximately represents component length and width in hundredths of an inch. For example:

- 0603 ≈ 0.06 × 0.03 inch
- 0805 ≈ 0.08 × 0.05 inch
- 1206 ≈ 0.12 × 0.06 inch

Metric and imperial codes should not be confused. An imperial 0603 package, for example, corresponds to metric 1608 rather than metric 0603.

Package size also affects manufacturability. Moving from 0805 or 0603 to 0402, 0201, or smaller parts generally requires tighter control of:

- PCB pad dimensions
- solder paste volume
- stencil apertures
- placement accuracy
- component spacing
- automated optical inspection
- rework

The smallest surface mount resistor is therefore not automatically the best choice. Use a smaller package when PCB density requires it, not simply because the package is available.

## How Do You Read Surface Mount Resistor Codes and Markings?

Surface mount resistor markings use numbers and letters to represent resistance because the component body is too small for traditional color bands. The most common surface mount resistor code systems are 3-digit codes, 4-digit codes, R notation, and EIA-96.

![Surface mount resistor codes and markings showing 3-digit, 4-digit, R notation and EIA-96 examples](https://www.bestpcbs.com/blog/wp-content/uploads/2026/09/surface-mount-resistor-codes-markings.jpg)
**3-digit surface mount resistor code**

The first two digits are significant figures. The third digit tells you how many zeros to add.

Code
Calculation
Value

101
10 × 101
100 Ω

102
10 × 102
1 kΩ

103
10 × 103
10 kΩ

331
33 × 101
330 Ω

472
47 × 102
4.7 kΩ

**4-digit surface mount resistor code**

The first three digits are significant figures and the fourth digit is the multiplier.

Examples:

- `1001` = 100 × 101 = 1 kΩ
- `4701` = 470 × 101 = 4.7 kΩ
- `1002` = 100 × 102 = 10 kΩ
- `4702` = 470 × 102 = 47 kΩ

Four-digit markings are often found on tighter-tolerance resistor series.

**R notation**

For low resistance values, `R` is used as the decimal point.

Examples:

- `R10` = 0.10 Ω
- `R47` = 0.47 Ω
- `2R2` = 2.2 Ω
- `4R7` = 4.7 Ω

**EIA-96 resistor markings**

EIA-96 uses two digits followed by a letter. The two-digit number refers to one of 96 standard base values, while the letter gives the multiplier.

Because the number is a lookup code rather than the resistance itself, an EIA-96 surface mount resistor code chart or calculator is usually the quickest way to decode it.

**Unmarked surface mount resistors**

01005, 0201, and some other small resistors may have no readable top marking. Their value should be identified using:

- BOM data
- manufacturer part number
- reel label
- assembly records
- resistance measurement

Appearance alone is not enough because different values can use identical packages.

## Surface Mount Resistor Values: What Do 100, 101, 102 and 103 Mean?

For a standard 3-digit surface mount resistor marking, the first two digits give the significant value and the third digit gives the multiplier.

![Common SMD resistor code values including 100, 101, 102, 103 and 331](https://www.bestpcbs.com/blog/wp-content/uploads/2026/09/surface-mount-resistor-values.jpg)

Surface Mount Resistor Code
Resistance Value

100
10 Ω

101
100 Ω

102
1 kΩ

103
10 kΩ

221
220 Ω

331
330 Ω

472
4.7 kΩ

104
100 kΩ

The code `100` is particularly easy to misread.

`100` means:

10 × 100 = 10 Ω

It does not normally mean 100 Ω.

A 100 ohm surface mount resistor commonly uses the code `101`:

10 × 101 = 100 Ω

Other common examples are:

- `102` surface mount resistor = 1 kΩ
- `103` surface mount resistor = 10 kΩ
- `331` surface mount resistor = 330 Ω
- `472` surface mount resistor = 4.7 kΩ

For example, a standard 330 ohm 0805 surface mount resistor may carry the marking `331` when that resistor series uses body markings.

## How Do You Choose the Right Surface Mount Resistor for a PCB?

Choose a surface mount resistor by checking the required resistance first, then tolerance, power, voltage, temperature behavior, pulse load, and package size.

The main specifications are:

- Resistance: Match the nominal value required by the circuit.
- Tolerance: ±5% and ±1% are common; precision designs may need ±0.5%, ±0.1%, or tighter.
- Power rating: Calculate actual dissipation and leave suitable operating margin.
- Working voltage: Check this separately from wattage, especially in high-voltage circuits.
- TCR: Use a lower temperature coefficient when resistance stability over temperature matters.
- Pulse rating: Check surge capability for startup, switching, discharge, and transient loads.
- Package: Select a size that meets both electrical and PCB space requirements.
- Availability: Check whether the exact series is practical to source throughout production.

Resistor power can be estimated using:

P = I2R

P = V2 / R

Package wattage should not be treated as a universal limit. The usable power also depends on the exact resistor series, ambient temperature, PCB copper area, and manufacturer derating curve.

Package selection also affects assembly. An electrically suitable 0201 resistor may be unnecessary if an 0603 fits comfortably and the product does not require extreme component density.

For production PCBs, the preferred package is usually the smallest size that meets the electrical and layout requirements without adding unnecessary assembly difficulty.

## Surface Mount Resistor vs Through-Hole Resistor: Which Should You Use?

The surface mount resistor vs through hole choice depends on assembly method, PCB area, mechanical needs, and power requirements. A surface mount resistor is usually preferred for compact and automated PCB assembly, while a through-hole resistor remains useful when easy manual handling, mechanical retention, or certain high-power requirements matter more.

![Surface mount resistor versus through-hole resistor comparison on printed circuit boards](https://www.bestpcbs.com/blog/wp-content/uploads/2026/09/surface-mount-vs-through-hole-resistor.jpg)

Factor
Surface Mount Resistor
Through-Hole Resistor

PCB area
Smaller
Larger

Automated assembly
Well suited
Less efficient

Component density
Higher
Lower

Lead inductance
Lower
Higher

Manual soldering
More difficult
Easier

Mechanical retention
Lower
Stronger

Rework
Harder at small sizes
Usually easier

High-density PCB
Preferred
Less suitable

Choose a surface mount resistor when the design prioritizes:

- compact PCB size
- automated SMT production
- high component density
- short electrical paths
- double-sided component placement

Choose a through-hole resistor when the design benefits more from:

- manual assembly
- straightforward repair
- stronger mechanical retention
- large leaded power components
- simple prototype construction

For most modern volume-produced PCB assemblies, surface mount resistors are the default choice.

## FAQs About Surface Mount Resistors

**1. What does 102 mean on a surface mount resistor?**

`102` means 1 kΩ. The first two digits are 10, and the third digit adds two zeros: 10 × 100 = 1,000 Ω.

**2. What does 103 mean on a surface mount resistor?**

`103` means 10 kΩ: 10 × 1,000 = 10,000 Ω.

**3. Is an 0805 resistor always 1/8 watt?**

No. Around 0.125 W is a common conventional rating, but the actual rating depends on the resistor series, construction, temperature, and manufacturer.

**4. What is the smallest surface mount resistor size?**

01005-class and smaller specialized resistors are available. The smallest practical package for a PCB depends on placement capability, stencil printing, inspection, rework, and required production yield.

**5. Why do some surface mount resistors have no markings?**

Small packages may not have enough body area for readable markings. Their resistance should be verified from the BOM, reel label, manufacturer part number, or measurement.

**6. Is an SMD resistor the same as an SMT resistor?**

In everyday use, the terms often refer to the same type of component. Technically, SMD means surface-mount device, while SMT is the manufacturing technology used to assemble it.

If you are preparing a PCB or PCBA project and need support with component package selection, SMT manufacturability, stencil design, or assembly planning, send your Gerber files, BOM, and assembly requirements to **[sales@bestpcbs.com](mailto:sales@bestpcbs.com)**