Ephemeral Port Range Calculator

Work out ephemeral port range instantly with clear inputs, formula shown and shareable results.

About Ephemeral Port Range Calculator

Each outbound connection consumes a local port for its lifetime plus the TIME_WAIT period, so the sustainable connection rate is port count divided by TIME_WAIT duration. The Linux default of 32768 to 60999 gives 28,232 ports, capping a single source-destination pair at roughly 470 new connections per second with a 60-second TIME_WAIT.

Formula

Port budget

ports = end - start + 1; required = connection rate x TIME_WAIT; max rate = ports / TIME_WAIT

Worked example

With the default values below, Ephemeral Port Range Calculator returns Ephemeral ports available of 28,232. Change any input above and every figure here is recalculated in your browser.

Inputs used

Range startaccepts 1,024–65,000: 32,768
Range endaccepts 1,025–65,535: 60,999
Outbound connections per secondminimum 0.001: 4,000
TIME_WAIT durationaccepts 1–240 s: 60 s

Results

Ephemeral ports available: 28,232
Ports needed at this rate: 240,000
Maximum sustainable connection rate: 471 conn/s
Assessment: Port exhaustion - widen the range, shorten TIME_WAIT or reuse connections

Step by step

1Values used
2Port budget
3Ephemeral ports available= 28,232
4Ports needed at this rate= 240,000
5Maximum sustainable connection rate= 471 conn/s
6Assessment= Port exhaustion - widen the range, shorten TIME_WAIT or reuse connections

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 whole numbers, 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

Is the limit really per source address?

The tuple is source IP, source port, destination IP and destination port, so the limit applies per destination pair. Many distinct destinations relieve the pressure; one busy upstream does not.

What is the best fix?

Connection reuse through keep-alive, which eliminates most port churn entirely. Widening the range and adding source addresses are secondary measures.