Inductors use two separate naming worlds, and mixing them up gets the wrong part on your board. Small chip inductors follow the EIA case codes you know from resistors (0402, 0603, 0805), while power inductors use manufacturer series codes that bury the footprint and height in the part number. This guide decodes both, gives real datasheet dimensions and currents, and shows why the inductor package size fixes the envelope but the inductance value decides how much current fits inside it.
[IMAGE 1: chip inductor case codes 0402 through 1210 drawn to scale beside a power inductor series (Coilcraft XAL, Taiyo Yuden NR) with dimensions labeled | alt: “Inductor package sizes to scale: chip case codes 0402-1210 and power inductor series with footprint and height dimensions”]
Key takeaways
- There are two systems: EIA chip case codes (0402 = 1.0 × 0.5 mm) for signal/RF parts, and manufacturer series codes (Coilcraft XAL, Taiyo Yuden NR) for power parts.
- Power-inductor codes usually encode footprint and height: Coilcraft XAL4020 is 4.0 × 4.0 mm with a 2.0 mm profile; Taiyo Yuden NR3015 is 3.0 × 3.0 × 1.5 mm.
- Same case size, different specs. In the 3.0 × 3.0 × 1.5 mm NR3015, a 22 µH part gives 0.47 A / 0.624 Ω DCR while a 2.2 µH part gives 1.5 A / 0.072 Ω, per Taiyo Yuden data.
- Isat is not defined the same way everywhere. Coilcraft rates Isat at a 30% inductance drop; other vendors use 10% or 20%, so cross-vendor comparison needs the same criterion.
- Height is a first-class dimension. One footprint often ships in several profiles — Vishay’s IHLP1212 comes in 1.2, 1.5, and 2.0 mm heights on the same 3.0 × 3.0 mm land.
The two inductor naming systems
Inductor package sizing is less standardized than resistors or capacitors. Chip inductors use EIA case codes — four digits encoding body length and width, like 0402 or 0805. Power inductors use manufacturer series names whose digits usually encode the footprint and height, like XAL4020 or NR3015. The code tells you the physical size; the electrical rating still comes from the datasheet.
That split matters because the two systems answer different questions. A chip case code describes a body you can compare across vendors dimensionally. A power series code points to one manufacturer’s specific footprint, and the “same” number from another vendor may differ. Get the system right first, then decode within it.
Chip and RF inductor case codes
Chip inductors — multilayer ferrite and small wirewound parts for RF, filtering, and matching — follow the EIA imperial code. The first two digits are body length in hundredths of an inch, the last two are width. So 0603 is 0.060 × 0.030 in ≈ 1.6 × 0.8 mm, and its metric name is 1608.
| Imperial | Metric | Body (mm) | Typical use |
| 0201 | 0603 | 0.6 × 0.3 | Ultra-compact RF, wearables |
| 0402 | 1005 | 1.0 × 0.5 | RF matching, high-density |
| 0603 | 1608 | 1.6 × 0.8 | General signal/RF |
| 0805 | 2012 | 2.0 × 1.25 | Filtering, small power |
| 1008 | 2520 | 2.5 × 2.0 | Higher-Q RF, small power |
| 1210 | 3225 | 3.2 × 2.5 | Power chip inductors |
| 1812 | 4532 | 4.5 × 3.2 | Higher-current chip power |
The same imperial/metric collision that bites passives applies here: imperial 0402 (1.0 × 0.5 mm) is not metric 0402 (0.4 × 0.2 mm), which is imperial 01005. Read the datasheet’s units. Panasonic’s ELJ-RF series, for example, is a 0402 (1.0 × 0.5 mm) RF chip inductor spanning roughly 1 nH to tens of nH, per its datasheet.
Inductance value is marked separately, usually with a three-digit code: 100 means 10 µH (two significant digits plus a zero-count multiplier), while 4R7 means 4.7 µH and R47 means 0.47 µH, using “R” as a decimal point, per SMD marking references. A dot on one end marks the winding start where polarity matters.
Power-inductor series codes
Power inductors carry current for DC-DC converters, so they are larger, and each manufacturer names them its own way. The useful pattern: the digits usually encode footprint and height in millimeters.
Coilcraft’s molded XAL family is a clear case. XAL4020 is a 4.0 × 4.0 mm footprint with a 2.0 mm profile; XAL6060 is 6.0 × 6.0 mm and 6.0 mm tall; XAL1350 is a 13.5 mm-class body. Taiyo Yuden’s NR3015 is 3.0 × 3.0 mm with a 1.5 mm height. Vishay’s IHLP and Bourns’ SRP/SRN work similarly, though prefixes and exact conventions differ.
| Series (vendor) | Footprint L × W | Height | Construction |
| NR3015 (Taiyo Yuden) | 3.0 × 3.0 mm | 1.5 mm | Ferrite drum, semi-shielded |
| SRN3015 (Bourns) | 3.0 × 3.0 mm | 1.5 mm | Ferrite drum, semi-shielded |
| IHLP-1212 (Vishay) | 3.0 × 3.0 mm | 1.2 / 1.5 / 2.0 mm | Iron-powder composite, shielded |
| XAL4020 (Coilcraft) | 4.0 × 4.0 mm | 2.0 mm | Metal-composite molded, shielded |
| XAL6060 (Coilcraft) | 6.0 × 6.0 mm | 6.0 mm | Metal-composite molded, shielded |
| SRP1245A (Bourns) | ~12.5 × 12.5 mm | 4.5 mm | Carbonyl powder, shielded |
Two construction families dominate. Ferrite drum-core wirewound parts (NR, SRN) are inexpensive with a sharper saturation knee, often semi-shielded. Metal-composite molded parts (Coilcraft XAL, Vishay IHLP, Bourns SRP) use iron or carbonyl powder in a resin binder, giving soft saturation, high current, and magnetic shielding — Vishay states IHLP is an iron-powder-and-resin mixture pressed around the coil, per its datasheet.
Even within one manufacturer the size code can change between families. Vishay alone uses different conventions for its IMC, ISC, IHSM, and IHLP series — the IHSM high-current line, for instance, uses codes like 3825 (0.38 × 0.25 in), per Vishay’s datasheet. There is no single cross-vendor inductor case-code standard, which is exactly why the datasheet is the authority.
[IMAGE 2: annotated Coilcraft XAL4020 part number showing 40 = 4.0 mm body, 20 = 2.0 mm height | alt: “Power inductor code decoded: Coilcraft XAL4020 digits encode 4.0 mm footprint and 2.0 mm height”]
Same case size, different specs
Package size sets the box; inductance value decides how much current fits inside it. Within one case size, raising inductance means more turns in the same volume, which raises DC resistance and lowers the saturation current.
Take the Taiyo Yuden NR3015 family, all in the same 3.0 × 3.0 × 1.5 mm body. The 22 µH NR3015T220M rates about 0.47 A with 0.624 Ω DCR, while the 2.2 µH NR3015T2R2M rates roughly 1.5 A with 0.072 Ω DCR, per distributor datasheet data. Ten times the inductance costs about three times the current capacity and nearly nine times the DCR — in an identical footprint.
The design lesson: choosing a package size does not choose your operating point. You pick the size for board area and height, then select the inductance value that still meets your current and DCR targets in that size. If it does not fit, you step up a size.
Height deserves its own attention. A single footprint frequently ships in multiple profiles: Vishay’s IHLP1212 offers 1.2, 1.5, and 2.0 mm heights on the same 3.0 × 3.0 mm land, per Vishay. Under a shield can or in a card-edge module, the profile can be the binding constraint, not the footprint.
Size versus current, DCR, and SRF — and the Isat trap
Bigger packages generally win on the specs that matter for power: more copper and core volume mean lower DCR, higher Irms (thermal current), and higher Isat (saturation current). Smaller packages win on area and often on self-resonant frequency for signal use.
Two current ratings are not interchangeable. Isat is the DC current at which inductance collapses by a defined percentage; Irms is the current that produces a defined temperature rise. Coilcraft defines Isat as the current causing a 30% inductance drop and Irms as the current for a specified temperature rise from 25 °C ambient, tested on 0.75 in × 0.25 in copper traces, per its documentation.
Here is the trap: vendors define Isat at different inductance-drop thresholds — commonly 10%, 20%, or 30%. Two “10 A Isat” parts are not equal if one is measured at a 10% drop and the other at 30%. Before you compare saturation ratings across manufacturers, normalize to the same drop criterion, or the comparison is meaningless. The same caution applies to Irms, which depends heavily on the test board and airflow the vendor used.
Master comparison table
| Package / series | Dimensions L × W × H (mm) | Construction | Current class | Typical use |
| 0402 chip | 1.0 × 0.5 × ~0.5 | Multilayer / thin-film | mA | RF, matching, filtering |
| 0805 chip | 2.0 × 1.25 × ~1.0 | Multilayer / wirewound | 100s mA | Signal, small power |
| 1210 chip | 3.2 × 2.5 × ~2.0 | Wirewound / molded | ~1 A | Power chip, filtering |
| NR3015 | 3.0 × 3.0 × 1.5 | Ferrite drum | ~0.5–2 A | Compact DC-DC |
| IHLP-1212 | 3.0 × 3.0 × 1.2–2.0 | Iron-powder molded | few A | Low-profile DC-DC |
| XAL4020 | 4.0 × 4.0 × 2.0 | Metal-composite molded | few A | High-freq buck |
| XAL6060 | 6.0 × 6.0 × 6.0 | Metal-composite molded | 10s A | High-current buck |
| SRP1245A | ~12.5 × 12.5 × 4.5 | Carbonyl powder | 10s A (Isat to ~118 A) | Automotive, high power |
How to choose an inductor package size
Work the decision in this order.
- Split by role. Signal, RF, or filtering points to chip case codes. Power conversion points to a molded or drum-core power series.
- Set your current first. Confirm the part’s Isat clears your peak current and its Irms clears your RMS current, both at your ambient — and check the Isat drop criterion.
- Fit the footprint and height. Choose the smallest package that meets current and DCR, then confirm the profile fits under any shield or enclosure.
- Check DCR against your efficiency budget. For power stages, keep DCR low enough that I²R loss and self-heating stay within target; step up a size if not.
- Confirm construction and shielding. Metal-composite molded parts give soft saturation and low EMI; unshielded drum cores are cheaper but radiate more.
[IMAGE 3: decision-path flowchart from role through current, footprint/height, DCR, to a package family | alt: “Inductor package size selection flowchart: role, current rating, footprint and height, DCR, construction”]
Second-source and cross-vendor hazards
“Equivalent” inductors in the same case size are rarely identical. The 3.0 × 3.0 × 1.5 mm body ships as Taiyo Yuden NR3015, Bourns SRN3015, and Vishay IHLP1212, but their inductance ranges, DCR, Isat criteria, and land patterns differ. A Bourns SRN3015 at 1.0 µH rates about 2.35 A with 48 mΩ DCR and a 145 MHz SRF, per distributor data — close to, but not the same as, a Taiyo Yuden part of the same size and value.
Footprints differ even when bodies match. Vishay notes its IHLP terminals are plated on the bottom and sides to form an inspectable solder fillet, while its IHLL terminals are plated on the bottom only for a smaller land, per Vishay. Swapping between them changes the land pattern and the stencil. For automotive, confirm AEC-Q200 qualification — Bourns’ SRP automotive series is AEC-Q200 qualified with footprints from 4.5 × 4.1 to 13.5 × 12.5 mm, per its product bulletin. Qualify the specific part and its land pattern, not just the nominal case size.
Design mistakes that cause failures
- Comparing Isat across vendors blindly. A part rated at a 10% drop looks stronger than one rated at 30%. Normalize the criterion before you trust the number.
- Sizing to Irms and ignoring Isat. A part that runs cool can still saturate on peak current, collapsing inductance and spiking ripple. Check both.
- Ignoring the datasheet land pattern. Two “0805” inductors can want different pads. Use the datasheet’s recommended footprint, not a generic library part.
- Overrunning the height budget. The footprint fits but the profile hits a shield or card spacing. Confirm the height variant early.
- Underrating DCR loss. Pushing inductance up in a small case raises DCR, wasting efficiency and heating the part. Step up a size instead.
- Using an unshielded part near sensitive nodes. Drum-core inductors radiate; keep them away from feedback and RF traces, or choose a shielded molded part.
FAQ
What are the standard SMD inductor sizes?
Chip inductors use EIA case codes — 0201, 0402, 0603, 0805, 1008, 1210, and 1812 — where the digits are body length and width in hundredths of an inch. Power inductors instead use manufacturer series codes like Coilcraft XAL or Taiyo Yuden NR, whose digits usually encode the footprint and height in millimeters.
What does 0805 mean on an inductor?
0805 is an EIA imperial case code: 0.08 × 0.05 in, about 2.0 × 1.25 mm body. The metric equivalent is 2012. It describes the physical size only — inductance, current rating, and DCR still come from the datasheet, and footprints can vary slightly between manufacturers for the same code.
Are inductor case codes the same as resistor case codes?
The chip code system is shared — 0402, 0603, and 0805 mean the same body dimensions. But inductor sizing is less standardized overall: power inductors use manufacturer series codes with no cross-vendor standard, and even chip-inductor footprints vary more than resistors, so always confirm against the datasheet.
What is the difference between Isat and Irms?
Isat is the DC current at which inductance drops by a defined percentage, so exceeding it collapses the inductor and spikes ripple. Irms is the current that causes a defined temperature rise, a thermal limit. You must satisfy both — Isat for peak current, Irms for continuous RMS current — at your operating ambient.
Does a bigger inductor package handle more current?
Generally yes. A larger package has more copper and core volume, giving lower DCR and higher Isat and Irms. Within one size, though, higher inductance means more turns, which raises DCR and lowers saturation current. So size sets the ceiling, and the inductance value you pick determines where you land under it.
How do I read an SMD inductor code?
Read two things. The size code (0805 or a series name) gives the physical package. The value code gives inductance: 100 means 10 µH, 4R7 means 4.7 µH, and R47 means 0.47 µH, with “R” as a decimal point. A dot marks the winding start. For everything else — current, DCR, tolerance — consult the datasheet.
The bottom line
Decide which naming world you are in before you read a single dimension. For signal and RF, use the EIA chip codes and match the footprint to the datasheet. For power, decode the series code to a real footprint and height, then size to current: confirm Isat clears your peak and Irms clears your RMS, both at the same drop and temperature-rise criteria the datasheet used. Choose the smallest package that still meets your DCR and height budget, and when you second-source, qualify the specific part and its land pattern — the case code alone does not guarantee a match.
Internal links: electronic component packages (types overview) · IC package naming conventions decoded · IPC-7351 land patterns · AEC-Q200 passive qualification · buck converter inductor selection.
External primary sources: Coilcraft XAL molded power inductors (coilcraft.com); Vishay IHLP power inductors (vishay.com); Bourns SRP series bulletin (bourns.com); Taiyo Yuden NR series datasheet (ty-top.com); Panasonic ELJ-RF chip inductor datasheet (panasonic).
