VoIP bandwidth calculator

Use this calculator to estimate how much upload and download capacity your calls may need. You only need the busiest number of calls, the codec, and a safety reserve.

VoIP bandwidth calculator

This estimate covers voice traffic in each direction. It assumes 20 ms packets, IPv4, and common Ethernet, IP, UDP, and RTP overhead. Encryption, IPv6, VPNs, VLANs, tunnels, and different packet sizes can increase the rate. The reserve is for voice only, so leave more room for other traffic.

Last reviewed: 4 September 2026. Technical references: RFC 3551 and RFC 7587.

Calls at the same timeCodecG.711 — 100 kbps conservative planning rateG.722 — 100 kbps conservative planning rateOpus — 40 kbps variable-rate estimateG.729 — 32 kbps Ethernet planning estimateVoice safety reserve20% reserve30% reserve50% reserve

What to enter

1. Enter the largest number of calls that may happen at the same time. Do not enter the total number of phones.
2. Choose the codec used by your provider or phone system. If you are unsure, ask the provider.
3. Keep the 30% reserve unless your design calls for another value.

The result covers voice traffic in each direction. Leave extra capacity for normal internet use, video, busy periods, and backup links. Experts should also check packet size, encryption, tunnels, and a real test call.

Related: VoIP capacity planning, voice codecs, and QoS and call quality.