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VoIP bandwidth calculator

One call with the common G.711 codec needs 87.2 kbit/s up and the same down on an office network; G.729 needs 31.2. Choose your codec and how many calls run at once to see your total.

Codec

More settings: packet interval, network, IP version, encryption

Packet interval

Network

IP version

Encrypted audio (SRTP)

Each call needs87.2kbit/s up and the same down
5 calls at once
436 kbit/s each way
Plan for, with a fifth spare
545 kbit/s each way
Data per call
39.2 MB an hour each way
One packet: 218 bytes, 50 a second
  • Voice 160 B
  • RTP, UDP, IP 40 B
  • Ethernet 18 B

Fits 91 calls at once, keeping a fifth free.

Each direction, without Ethernet preamble and gap, VLAN tags or Wi-Fi framing. Everything runs in your browser.

kb

Bandwidth per call, by codec

Squeezing the voice saves less than you think. The headers stay.

Every packet carries 58 bytes of addressing whatever the codec. G.729 shrinks the voice to an eighth, and the call still needs over a third of G.711's bandwidth.

  1. G.711 (PCMU or PCMA)64.0 kbit/s of voice87.2
  2. G.72264.0 kbit/s of voice87.2
  3. G.7298.0 kbit/s of voice31.2
  4. Opus at 24 kbit/s24.0 kbit/s of voice47.2

voice headers. 20 ms packets, IPv4, Ethernet or Wi-Fi, kbit/s each way. Opus varies its bitrate from 6 to 510 kbit/s. 24 kbit/s is an example setting for voice, not a fixed value.

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How the number is worked out

Four steps, shown for G.711 in 20 ms packets.

  1. 1

    Voice per packet

    64,000 bit/s for 20 ms = 160 bytes

  2. 2

    Add the headers

    RTP 12 + UDP 8 + IPv4 20 + Ethernet 18 = 58 bytes

  3. 3

    Packets a second

    1,000 ms / 20 ms = 50

  4. 4

    Bandwidth

    218 bytes x 8 x 50 = 87.2 kbit/s each way

Longer packets save bandwidth and add delay. At 30 ms, G.711 drops to 79.5 kbit/s, but each packet waits 10 ms longer to fill. Most SIP trunks expect 20 ms.

!

When the bandwidth is fine and calls still sound bad

A fast line can still break up a call.

Choppy or robotic audio usually comes from packet loss, jitter or delay, which a speed test does not show. Find the cause in our SIP troubleshooting guide.

FAQ

VoIP bandwidth questions

How much bandwidth does one VoIP call use?
With G.711, about 87.2 kbit/s in each direction on Ethernet or Wi-Fi. G.729 needs about 31.2. The codec's own bitrate is lower; packet headers make up the rest.
How much upload do I need for 10 VoIP calls?
About 0.9 Mbit/s for ten G.711 calls, and more to keep spare for everything else on the line. Upload matters most, because it is usually the smaller number on broadband.
How much data does a VoIP call use per hour?
About 39 MB each way per hour with G.711, so roughly 78 MB in total. G.729 uses about 14 MB each way.
Does a VPN increase VoIP bandwidth?
Yes. A WireGuard tunnel adds 60 bytes or more to every packet, which takes a G.711 call from 87.2 to about 114 kbit/s. Other VPNs add similar or larger amounts.
Does encrypting calls use more bandwidth?
A little. SRTP with the common AES and SHA-1 profile adds a 10-byte tag to each packet, about 4 kbit/s on a G.711 call.

Bandwidth sorted. Now the trunk.

How channels, codecs and costs fit together: our SIP trunk guide. Prepaid calling with no contract: our prepaid SIP trunk provider page.

See the SIP trunkRead the SIP trunk guide