GTP Tunnel Calculator
Size GTP-U transport for a bearer population, including encapsulation overhead and packet-per-second load.
About GTP Tunnel Calculator
GTP-U wraps every user packet in an 8-byte GTP header, an 8-byte UDP header and a 20-byte outer IP header. Because that cost is per packet, the percentage overhead depends entirely on the average packet size — small-packet traffic such as signalling or gaming pays far more than bulk video. S1-U and N3 backhaul is dimensioned in Gbps but policed in packets per second, and forgetting 36 bytes of encapsulation is a reliable way to saturate a link at 96% of its nominal capacity.
Formula
GTP Tunnel
transport = user payload × (1 + header bytes ÷ average packet size); packet rate = payload bits ÷ (packet size × 8).
- header bytes
- GTP-U 8 + UDP 8 + outer IPv4 20 = 36
- payload
- bearers × average per-bearer rate
Worked example
With the default values below, GTP Tunnel Calculator returns Encapsulated Transport Load of 31.350. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Active bearersaccepts 1–50,000,000 bearers
- 200,000 bearers
- Average throughput per beareraccepts 1–1,000,000 kbps
- 150 kbps
- Average user packet sizeaccepts 64–9,000 bytes
- 800 bytes
- GTP-U + UDP + IP headeraccepts 8–100 bytes
- 36 bytes
Results
- Encapsulated Transport Load
- 31.350 Gbps
- User-Plane Payload
- 30.000 Gbps
- Encapsulation Overhead
- 4.50%
- Packet Rate
- 4.688 Mpps
Step by step
- 1Values used
- 2GTP Tunnel
- 3Encapsulated Transport Load= 31.350 Gbps
- 4User-Plane Payload= 30.000 Gbps
- 5Encapsulation Overhead= 4.50
- 6Packet Rate= 4.688 Mpps
Assumptions and limits
- The result is derived only from the 4 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 3 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
How is GTP Tunnel calculated?
transport = user payload × (1 + header bytes ÷ average packet size); packet rate = payload bits ÷ (packet size × 8). GTP-U wraps every user packet in an 8-byte GTP header, an 8-byte UDP header and a 20-byte outer IP header. Because that cost is per packet, the percentage overhead depends entirely on the average packet size — small-packet traffic such as signalling or gaming pays far more than bulk video.
Why does GTP Tunnel matter?
S1-U and N3 backhaul is dimensioned in Gbps but policed in packets per second, and forgetting 36 bytes of encapsulation is a reliable way to saturate a link at 96% of its nominal capacity.
What values do I need to enter?
This calculator takes 4 inputs: Active bearers, Average throughput per bearer, Average user packet size, GTP-U + UDP + IP header. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.