The Resistor Code: Deciphering Sizes and Packages

By Srikanth
5 Min Read
The Resistor Code: Deciphering Sizes and Packages 1

Although resistors may appear to be small components, their shapes and sizes play a significant role in electronics. This guide covers Surface Mount, Through-Hole Mount, and MELF resistors. We will also learn about SMD and THT resistors and their sizes. Whether you are an electronics enthusiast or just curious about how things work, this article will help you understand those small but essential components.


Categories Of Resistor Code Packages

There are two main types of resistor packages:

  • Surface Mount
  • Through-Hole Mount

1. Through-Hole Mount Or DIP

It takes a lot of space on the circuit board to install the component, which is considerable. The component is put in after the drilling, and then the tin furnace or spraying (also called hand soldering) is expensive.

2. Surface Mount Or SMD

You do not have to drill holes for this type of component. Instead, fill the circuit board with partially melted solder paste using a steel film, then top it off with the SMD component. Solder the board with solder. Each kind of resistor has different properties regarding power and volume. It generally has more power the higher the volume.

Resistors come in a wide variety of sizes and package types. Rectangular surface mount (SMD) resistors are more frequently used in through-hole designs, though axial resistors are still utilised frequently. Details regarding SMD, axial, and MELF package sizes are available on this page. Furthermore, it provides some recommended land patterns for SMD components soldered to PCBs.

What Determines The Size Of A Resistor?

The Resistor Code: Deciphering Sizes and Packages 2

Most of the time, the amount of heat the resistor can safely lose (without burning) determines its size. High-temperature resistors usually have a rectangular cuboid shape, like a rectangle, but in three dimensions. People often call high-wattage resistors that can change their resistance “rheostats.”

SMD Resistor Sizes

Most manufacturers use the JEDEC standards to ensure that surface mount resistors are all the same size and shape. A number code, like 0603, tells you what size SMD resistor it is. The length and width of the package are in this code. This means that the imperial code 0603 has a length of 0.060″ and a width of 0.030″. You can give the SMD package code in either metric or imperial units. Most of the time, the imperial code is used to show the size of the package. It can be confusing because metric measurements are often used when designing printed circuit boards (PCBs), even when imperial names are used.

MELF Resistor

The acronym for metal electrode leadless face is MELFF. This surface mount resistor package is distinct. Compared to standard SMD packages, MELF packages have more stable and lower thermal coefficients. Compared to thick film SMD resistors, which have temperature coefficients (TCR) of more than 200 ppm/K, thin film MELF resistors have 25 to 50 ppm/K TCRs.

MELF resistors have a lower TCR because of their cylinder shape. The cylindrical shape of the package presents particular challenges when using pick-and-place machines to place the components. It requires specialised suction cups and greater hoover because of its round shape. The three most popular MELF package sizes are MegaMELF, MiniMELF, and MELF. These types and their descriptions are listed in the table below.

THT Resistors

However, THT resistors are not standardized like SMD resistors are, and different manufacturers may use slightly different measurements. You can also tell the size of a THT resistor by its type, such as carbon material, wire wound, carbon film, or metal film, and how much power it can handle. The length of a 1/4W resistor is only 6.3mm, while the width of a standard 1/2W resistor is 9.2mm. If you need to know a part’s exact size, look at the manufacturer’s datasheet.


Electronics workers must understand resistor sizes and packages. Understanding resistor dimensions and power ratings, whether variable THT or compact SMD resistors that meet JEDEC standards, can make or break a circuit. MELF resistors have unique benefits and drawbacks. Next time, you will understand the resistors’ role when you play with electronics. To explore electronic components one resistor at a time, visit our website PartStack for more exciting content and electronic solutions!

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