A crystal or oscillator package size is written as a four-digit code — 3225, 5032, 7050 — that encodes length by width in tenths of a millimeter, so a 3225 measures 3.2 mm × 2.5 mm. That code is all most datasheets shout, yet it hides the two things that decide whether a part fits your board and your oscillator circuit: height and pad count. This guide maps every mainstream crystal and oscillator package size to real dimensions, with verified example parts, and shows what you trade away each time you go smaller.

Key takeawaysThe four-digit code is length × width in tenths of a mm — it does not tell you height or pin count. Read those separately from the datasheet.A passive crystal (resonator) has 2 pads; an active oscillator integrates an IC and uses 4 pads (single-ended) or 6 (differential), pushing it into a larger package.3225 and 2520 are today’s workhorse MHz sizes; 3215 (3.2 × 1.5 mm) dominates 32.768 kHz; HC-49 survives where through-hole robustness matters.Shrinking raises ESR and tightens the oscillator’s gain margin — a smaller crystal is not a free swap.MEMS oscillators reach a 1.5 × 0.8 mm chip-scale package and drop into a 2.0 × 1.2 mm quartz footprint, opening sizes quartz cannot.The code is not a standardized land pattern — two ‘3225’ parts can want different footprints, so design to the specific outline drawing.

What a crystal package size code actually means

The numbering is a dimensional shorthand: read the four digits as two pairs, each pair a dimension in tenths of a millimeter. 3225 = 3.2 × 2.5 mm, 5032 = 5.0 × 3.2 mm, 7050 = 7.0 × 5.0 mm, 2520 = 2.5 × 2.0 mm, 2016 = 2.0 × 1.6 mm. The code covers only the footprint outline — height and pad count are separate specifications you must pull from the datasheet, and they vary within a single code. This is the one rule that unlocks every size chart below.

That gap matters immediately: a 3225 crystal might be 0.65 mm high, while a 5032 is typically 1.0 mm high — the code tells you neither. Two parts sharing a code can also differ in whether they are a bare 2-pad resonator or a 4-pad packaged part, which changes the land pattern entirely.

[IMAGE 1: Scaled outline drawings of 7050, 5032, 3225, 2520, 2016 and a 1.5 × 0.8 mm CSP side by side — alt: “Crystal and oscillator package sizes compared to scale from 7050 down to a 1.5 by 0.8 mm chip-scale package”]

Crystal vs oscillator: why pin count drives the package

The terms get used interchangeably, but they are different devices, and the difference sets the minimum package size.

A quartz crystal (resonator) is passive: a slab of quartz with two electrodes, 2 pads, no active circuitry. It needs an external oscillator circuit — typically an inverter inside your MCU plus two load capacitors — to actually oscillate. Because it is just the resonator, it packs into the smallest packages.

A crystal oscillator is active: it seals the resonator together with an amplifier and output stage in one package. A single-ended XO or TCXO needs four connections; a differential oscillator (LVDS, LVPECL, HCSL) needs six, so differential oscillators use the larger packages. That integrated IC is why an oscillator in a given size code is generally taller than a bare crystal in the same code, and why the smallest codes are populated mostly by resonators. Match the device type to your need first; the package size follows from it.

SMD crystal (resonator) package sizes — MHz

For megahertz timing references — the crystal feeding an MCU, radio, or USB PHY — these are the surface-mount sizes in current production. Dimensions are the code’s definition; heights and example parts are attributed where verified.

Package	L × W (mm)	Typical height (mm)	Pads	Verified example / note
1210	1.2 × 1.0	per datasheet	2	Space-critical designs; highest ESR of the group
1612	1.6 × 1.2	~0.5	2 / 4	Practical sub-2 mm floor for volume quartz
2016	2.0 × 1.6	per datasheet	2 / 4	Common small MHz footprint
2520	2.5 × 2.0	~0.55	2 / 4	A-Crystal P2SB: 12–80 MHz, AEC-Q200
3225	3.2 × 2.5	~0.65	2 / 4	A-Crystal: 7.37–80 MHz, AEC-Q200
5032	5.0 × 3.2	~1.0	2 / 4	A-Crystal: 7–70 MHz, AEC-Q200; lower ESR
6035	6.0 × 3.5	per datasheet	2 / 4	Legacy mid-size
7050	7.0 × 5.0	~1.0	2 / 4	A-Crystal P3SB: robust, low ESR
8045	8.0 × 4.5	per datasheet	2	Older glass-sealed format

The verified per-size data is from manufacturer datasheets: A-Crystal lists its 2520 (2.5 × 2.0 mm) at 0.55 mm high across 12–80 MHz, its 3225 (3.2 × 2.5 mm) at 0.65 mm, its 5032 (5.0 × 3.2 mm) at 1.0 mm for 7–70 MHz, and its 7050 (7.0 × 5.0 mm) at 1.0 mm, all AEC-Q200 compliant. Ceramic-package parts reach as small as 1.6 × 1.2 × 0.4 mm in specialty lines. For most new MHz designs, 3225 or 2520 is the right default — small enough for dense boards, large enough to keep ESR and sourcing sane.

32.768 kHz and through-hole packages

The 32.768 kHz “watch” crystal that clocks real-time counters is a tuning-fork resonator and lives in its own set of packages, because its mechanical structure is longer and narrower than an AT-cut MHz blank.

Package	L × W (mm)	Height (mm)	Verified example / note
1610	1.6 × 1.0	per datasheet	Smallest common quartz 32.768 kHz SMD
2012	2.0 × 1.2	per datasheet	Quartz 32k; also the MEMS drop-in footprint
3215	3.2 × 1.5	0.9 (0.38 low-profile)	Abracon ABS07 / ABS07L
Cyl 2 × 6	Ø2.0 × 6.0	—	Cylindrical can, SMD or radial
Cyl 3 × 8	Ø3.0 × 8.0	—	Older radial watch crystal
HC-49/US	11.05 × 4.65	~3.5–4.5	Low-profile through-hole MHz can
HC-49/U	11.05 × 4.65	~13.46	Full-height through-hole MHz can

The 3215 is the mainstream 32.768 kHz SMD size. Abracon’s ABS07 datasheet lists it at 3.2 × 1.5 mm, 0.9 mm high, with 70 kΩ ESR and tolerance options of ±10, ±20 and ±30 ppm over −40 to +85 °C; the low-profile ABS07L variant drops the height to 0.38 mm in the same footprint. On the through-hole side, the two HC-49 heights are the thing people confuse: an HC-49/U is the tall can at roughly 11.05 × 4.65 × 13.46 mm, while the HC-49/US is the low-profile version around 3.5–4.5 mm tall in the same length and width. Reach for HC-49 only when you genuinely need leaded robustness — socketed prototyping, high shock/vibration, or hand assembly.

[IMAGE 2: Side profile of HC-49/U tall can next to HC-49/US low-profile can — alt: “HC-49/U full-height crystal package next to the low-profile HC-49/US variant showing the 13.46 mm versus roughly 4 mm height difference”]

Oscillator (XO, TCXO, OCXO) package sizes

Active oscillators reuse the same four-digit codes but skew larger because of the integrated IC. XOs commonly span 2016 up to 7050. ECS’s ECS-2016MVQ, for example, is a 2016 (2.0 × 1.6 mm) HCMOS oscillator, 0.85 mm high, covering 1.5 to 54 MHz with ±20 to ±100 ppm stability and about 1 ps of phase jitter, AEC-Q200 qualified for Grade 1. TCXOs cluster a little larger: 5.0 × 3.2 × 1.5 mm and 5.0 × 3.5 × 1.0 mm are widely used, with smaller options where board space is tight.

OCXOs are a different world — the oven and thermal mass demand volume. High-stability oven oscillators run to packages on the order of 2 × 2 × 3 inches, with the most extreme lab-grade units around 3 × 3 × 5 inches, though modern surface-mount OCXOs are far smaller. If you need a differential output, budget for a 6-pad part and the larger footprint that comes with it.

MEMS oscillators: the sub-2 mm frontier

This is where quartz-centric guides go quiet. A MEMS oscillator seals a silicon resonator in a CMOS package, so it can use IC packaging quartz cannot — and it eliminates the external load capacitors, because it drives the chipset’s clock input directly.

SiTime’s SiT8021 ships in a chip-scale package measuring 1.5 × 0.8 mm, just 0.5 mm high — the industry’s smallest oscillator package — drawing about 100 µA at 1.8 V. For 32.768 kHz, the SiT1532/42 hits the same 1.5 × 0.8 mm chip-scale package at under 1 µA and a 1.2 mm² footprint, and its sibling SiT1533/43 comes in a 2.0 × 1.2 mm package that is pin-compatible with quartz resonators — a genuine drop-in. SiTime states the CSP delivers up to 85% board-area savings versus a 2012 package and about 70% versus the smallest sampling quartz package. For automotive, the SiT8924B is a 25 MHz MEMS oscillator in a 2.5 × 2.0 mm package, ±25 ppm, −40 to +125 °C, AEC-Q100 compliant. When you need a footprint below ~2 mm, a drop-in for a flaky quartz resonator, or high shock survivability, MEMS is the package play.

[IMAGE 3: A 1.5 × 0.8 mm MEMS CSP next to a 3215 quartz tuning-fork crystal at the same scale — alt: “1.5 by 0.8 mm MEMS chip-scale oscillator shown next to a 3.2 by 1.5 mm quartz 32.768 kHz crystal at the same scale”]

How small can you go? The ESR and drive-level tradeoff

Smaller is not free. As the quartz blank shrinks, its equivalent series resistance (ESR) climbs — the tiny 32.768 kHz 3215 parts above already sit at 70–80 kΩ. Higher ESR demands more from your oscillator circuit’s negative resistance: the usual rule of thumb is that the circuit’s negative resistance should exceed the crystal’s ESR by a comfortable margin (often cited around 5×) for reliable startup over temperature. Push the package too small without checking this and you get intermittent no-start units in the field.

Two more package-linked parameters to verify against the datasheet before committing to a size:

• Load capacitance (C_L). A crystal is specified for a given C_L, set by your two external caps and stray capacitance: C_L ≈ (C1 × C2) / (C1 + C2) + C_stray. The wrong capacitance value pulls the frequency off target or prevents oscillation entirely. Active oscillators sidestep this — no load caps.
• Drive level. Small blanks tolerate less power; overdriving accelerates aging and can crack the resonator.

The honest tradeoff: every step down in package size buys board area at the cost of ESR headroom, startup margin, and often frequency-stability grade. Size the package to the smallest that still leaves your startup margin and stability spec intact — not the smallest that exists.

Footprints and standards: the code is not a land pattern

A recurring field mistake is treating the package code as a footprint. It is not. The four-digit code fixes the body’s length and width, but pad geometry, keep-outs and thermal relief still come from the manufacturer’s outline drawing — two “3225” parts from different vendors can want slightly different land patterns. Pull the recommended footprint from the datasheet you are actually buying.

There are real standards behind these parts, they just aren’t a single JEDEC package spec. IEC 60122-1 is the generic specification for quartz crystal units, and IEC 60122-3 specifies standard outlines and lead connections for leaded units; SMD crystal enclosures are addressed under the IEC 61837 series, with quartz oscillators covered by IEC 60679. For automotive, watch the passive/active split: passive crystals are qualified to AEC-Q200, while active IC- or MEMS-based oscillators are qualified to AEC-Q100. AEC-Q200 was revised to Revision E in March 2023. Specifying “AEC-Q200” for an oscillator, or “AEC-Q100” for a bare crystal, is a common BOM-review reject.

Worked example: a space-constrained BLE wearable

Suppose you are laying out a wearable with an nRF-class BLE SoC that needs both a 32.768 kHz sleep clock and a MHz reference, and board area is brutal.

• MHz reference: start at 3225 (3.2 × 2.5 mm) as the safe default. If the layout can’t spare it, step to 2520 (2.5 × 2.0 mm) and re-check startup margin against the crystal’s ESR.
• 32.768 kHz sleep clock: a 3215 quartz (3.2 × 1.5 mm) at 12.5 pF C_L is the conventional pick. If the RTC is unreliable at temperature or you’re fighting for the last square millimeter, the SiT1533 MEMS in a 2.0 × 1.2 mm package drops into the quartz footprint, deletes both load caps, and frees area.
• If the whole design has to shrink again: the 1.5 × 0.8 mm MEMS CSP saves up to ~85% of the 2012 area — at a unit-cost premium over a jellybean quartz.

That sequence — default to a mainstream size, shrink only with the ESR/startup check, and jump to MEMS when quartz runs out of room — is the pattern that keeps you off the returns list.

Frequently asked questions

What do the numbers in a crystal package size mean?

They are the body’s length and width in tenths of a millimeter. A 3225 is 3.2 × 2.5 mm, a 5032 is 5.0 × 3.2 mm, a 7050 is 7.0 × 5.0 mm. The code omits height and pad count, which differ between parts sharing the same code, so read those from the datasheet.

What is the most common crystal package size?

For MHz crystals, 3225 (3.2 × 2.5 mm) and 2520 (2.5 × 2.0 mm) are today’s high-volume defaults, with 5032 and 7050 common in legacy and lower-ESR designs. For 32.768 kHz, 3215 (3.2 × 1.5 mm) dominates. HC-49 remains the standard through-hole can.

What is the difference between HC-49/U and HC-49/US?

Mainly height. Both are through-hole cans roughly 11.05 × 4.65 mm in footprint. The HC-49/U is the full-height version at about 13.46 mm tall; the HC-49/US is the low-profile version at roughly 3.5–4.5 mm. Choose HC-49/US when vertical clearance is limited but you still want leaded mounting.

Does a smaller crystal package hurt performance?

It can. Smaller quartz blanks have higher ESR, which shrinks the oscillator’s startup margin and can cause intermittent no-start over temperature. Smaller parts may also carry looser stability grades and tolerate less drive level. Pick the smallest package that still clears your negative-resistance margin and stability spec.

What package size is a 32.768 kHz crystal?

Most commonly 3215 (3.2 × 1.5 mm), around 0.9 mm high, with low-profile variants down to 0.38 mm. Smaller quartz options reach 2012 (2.0 × 1.2 mm) and 1610 (1.6 × 1.0 mm); cylindrical 2 × 6 mm cans are the legacy format.

Can a MEMS oscillator replace a quartz crystal?

Often yes. Parts such as SiTime’s SiT1533 come in a 2.0 × 1.2 mm package pin-compatible with quartz resonators and drive the chipset clock input directly, eliminating external load capacitors. MEMS also reaches sizes and robustness quartz cannot, at a higher unit cost. Verify frequency, stability and supply-voltage compatibility before swapping.

The decision

Default to 3225 or 2520 for a MHz crystal and 3215 for 32.768 kHz — they balance size, ESR, and sourcing. Reserve HC-49 for genuine through-hole robustness. Move to a MEMS package (2.0 × 1.2 mm drop-in, or the 1.5 × 0.8 mm CSP) when you need a sub-2 mm footprint, a fix for an unreliable resonator, or high shock survivability, and you can absorb the cost. Whatever code you choose, verify three things against the exact datasheet before release: ESR against your circuit’s startup margin, load capacitance, and the recommended land pattern. The code gets you to the right shelf; the datasheet gets you a board that starts every time.

Internal links to add: (1) load capacitance and crystal circuit design → C_L calculation guide; (2) choosing between a crystal and an oscillator → resonator-vs-oscillator selection; (3) AEC-Q100 vs AEC-Q200 for timing components → automotive qualification explainer. Swap for real fpga.io URLs.

External primary sources: Abracon ABS07/ABS07L datasheet & parametric pages; SiTime SiT1532 and SiT8021 datasheets and MEMS application note; ECS via DigiKey; IQD/NKG HC-49 datasheets; IEC standards index (60122, 61837, 60679); AEC-Q200 Rev-E references (CTS, AEC).