Ethernet Frame Size Calculator
Compute Ethernet II frame size, padding, on-the-wire size, overhead and efficiency from a payload size (or the reverse), with VLAN tags and an optional line rate.
This tool handles input and primary processing in your browser and is designed not to send the input to QuickKit’s server.
Frame breakdown
| Payload | — |
|---|---|
| Padding added | — |
| L2 header + FCS | — |
| L2 frame size | — |
| Size on the wire | — |
| Total overhead | — |
| Overhead | — |
| Efficiency | — |
| Size used for IEEE limit check (payload + tag overhead) | — |
| IEEE 802.3 size limit | — |
| Max frames per second | — |
| Max payload throughput | — |
“Baby giant” and “jumbo frame” are vendor terms with platform-dependent thresholds; IEEE 802.3 defines no such classifications, so this tool does not apply them to any size.
How it works
Computes Ethernet II frame sizes from a payload size, or the maximum payload / MTU from a frame size. This tool's "payload" is the original client data, before any VLAN tag; IEEE 802.3 bounds the MAC Client Data field, and to compare a frame against those bounds this calculator adds the tag overhead to the payload, so both that accounting size and the payload are shown; it is a size used for the limit check, not a claim that a tag sits inside the MAC Client Data field. An untagged frame adds 18 bytes (6+6 addresses, 2 EtherType, 4 FCS) and each 802.1Q tag adds 4 more. IEEE 802.3 clause 3.2.7 enumerates three MAC Client Data maxima and the frame sizes they imply: 1500 in a 1518-byte basic frame, 1504 in a 1522-byte Q-tagged frame, and 1982 in a 2000-byte envelope frame. IEEE 802.3as gives Q-tagged and envelope frames a larger MAC Client Data allowance than a basic frame — which is why the Q-tagged maximum is 1504 and not 1500 — so tagging raises the applicable limit instead of making a frame oversize. In this calculator, adding one VLAN tag increases the size used for the limit check by four octets, which matches the 1504-byte Q-tagged allowance and the 1522-byte frame maximum; a 1526-byte QinQ frame is likewise within the envelope limit. 1518, 1522 and 2000 are the standard's own numbers; 1526 is derived here from a 1500-byte payload plus two tags and is not a limit IEEE 802.3 names. IEEE 802.3 also notes that the original client data should stay within 1500 bytes even inside an envelope frame, which is reported separately when a payload exceeds it. IEEE 802.3 defines no "standard" versus "oversize" classification, and it defines neither "baby giant" nor "jumbo frame"; those are vendor terms whose thresholds differ by vendor and platform, so this tool never applies them to a size and only notes that they exist. Padding is added as needed to reach the 64-byte minimum frame size, so the payload size at which padding starts depends on the tag count — 46 bytes untagged, 42 with one tag, 38 with two. When "count preamble + SFD + IFG" is on (the default), the wire figure, overhead and efficiency all include the 7-byte preamble, 1-byte SFD and 12-byte interframe gap (20 bytes), so efficiency is payload / (frame + 20); frames-per-second and throughput at a selected line rate always count that 20-byte gap. Jumbo frames (commonly a 9000-byte payload, sometimes a 9216-byte frame limit on switches) are widely deployed but are not standardised by IEEE 802.3, and the sizes vendors accept vary. All computation runs locally in your browser.