How to Use This Tool
Subtract every modeled header from MTU before estimating payload efficiency and packet count. Calculate maximum application payload, MTU efficiency, packet count and modeled header bytes from MTU and protocol overhead.
The decision this tool supports
Engineers quote link MTU as usable application payload and then underestimate segmentation, header bytes and storage or latency overhead. This page keeps the decision bounded to maximum application payload and the supporting outputs shown beside it. MTU Payload Efficiency does not import an account, infer a market rate, or silently substitute an industry average.
Inputs and units
The MTU Payload Efficiency calculation uses Path MTU, IP header, Transport header, Additional per-packet overhead, Application data to transfer. Keep all money values in one currency and all time, distance, mass, energy or volume entries in the unit printed beside the field. Mixing MTU Payload Efficiency scopes can produce a plausible number with the wrong meaning.
- Path MTU is entered in bytes.
- IP header is entered in bytes.
- Transport header is entered in bytes.
- Additional per-packet overhead is entered in bytes.
- Application data to transfer is entered in bytes.
Formula and worked check
Maximum payload = MTU − modeled headers; packets = ceiling(application bytes ÷ payload); modeled header bytes = packets × header total. A 1,500-byte MTU with 62 bytes modeled overhead leaves 1,438 bytes payload, 95.9% MTU efficiency and 696 packets for 1,000,000 application bytes. The MTU Payload Efficiency default is an executable known-answer case, not a benchmark or recommendation. Change one input and verify that the direction of maximum application payload still matches the stated relationship.
How to interpret the result
Enter the exact IP, transport, tunnel and security overhead for the path; use packet captures to confirm negotiated behavior. The additional MTU Payload Efficiency outputs expose the denominator, comparison, capacity or reverse value needed to audit the primary result instead of presenting one unexplained number.
Assumptions
- All per-packet overhead is entered explicitly.
- No fragmentation or retransmission occurs.
- Application bytes are segmented to the calculated maximum payload.
Save the MTU Payload Efficiency input values and date with any material decision. A later MTU Payload Efficiency rerun is reproducible only when the same assumptions and units are available.
Limitations and safety boundary
The model excludes variable headers, retransmission, fragmentation, offload, padding, link-layer overhead, congestion and middlebox behavior. MTU Payload Efficiency is an estimate and cannot replace a contract, local code, licensed professional, calibrated measurement, lender statement or platform report where one governs the decision.
Source and privacy
The MTU Payload Efficiency definition or rule was checked against IETF RFC 8200 — IPv6 Specification on 2026-08-26. Recheck IETF RFC 8200 — IPv6 Specification when a specification or policy behind MTU Payload Efficiency can change. MTU Payload Efficiency arithmetic runs in this browser tab; ecech does not receive the values through a calculation API.
Sources & assumptions
Tool Spec v2 · verified 2026-08-26. Platform rules and fees can change; the editable inputs remain authoritative for your account.
Official references
- IETF RFC 8200 — IPv6 Specification (checked 2026-08-26)
Model assumptions
- All per-packet overhead is entered explicitly.
- No fragmentation or retransmission occurs.
- Application bytes are segmented to the calculated maximum payload.
- The model excludes variable headers, retransmission, fragmentation, offload, padding, link-layer overhead, congestion and middlebox behavior.
