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Fragmentation Overhead Calculator

Work out fragmentation overhead instantly with clear inputs, formula shown and shareable results.

About Fragmentation Overhead Calculator

IPv4 fragmentation splits the payload into chunks whose size must be a multiple of eight bytes, and each fragment carries its own 20-byte header. The byte overhead is modest but the packet-rate increase is not: doubling packets per second doubles the interrupt and forwarding-table work, and losing any single fragment destroys the entire original datagram.

Formula

Fragmentation

payload per fragment = floor((MTU - 20) / 8) x 8; fragments = ceil(payload / payload per fragment); overhead = fragments x 20 - 20

Worked example

With the default values below, Fragmentation Overhead Calculator returns Fragments per original packet of 2. Change any input above and every figure here is recalculated in your browser.

Inputs used

Original packet sizeaccepts 64–65,535 bytes
1,500 bytes
Smallest MTU in the pathaccepts 576–9,216 bytes
1,400 bytes
Packet rateminimum 1 pps
50,000 pps

Results

Fragments per original packet
2
Extra header bytes per packet
20 bytes
Additional packets per second created
50,000 pps
Byte overhead added
1.33%

Step by step

  1. 1Values used
  2. 2Fragmentation
  3. 3Fragments per original packet= 2
  4. 4Extra header bytes per packet= 20 bytes
  5. 5Additional packets per second created= 50,000 pps
  6. 6Byte overhead added= 1.33

Assumptions and limits

  • The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Why is losing one fragment so costly?

The receiver cannot reassemble the datagram, so every fragment already received is discarded. Effective loss is multiplied by the fragment count.

Does IPv6 fragment?

Not in routers. Only the source may fragment, using an extension header, and routers drop oversized packets with a Packet Too Big message instead.

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