How to use this calculator
- Enter the busiest expected simultaneous call count.
- Select or enter the codec payload bitrate.
- Add packetization overhead and signaling allowance.
- Keep a reserve for bursts and growth, then calculate.
#3104 · AI & Technology Tool
VoIP System Bandwidth Requirement Calculator
Size a voice network from simultaneous calls rather than total extensions. The calculator converts codec payload rate into provisioned bandwidth per call, adds signaling and operational reserve, and reports the required capacity in each direction. Use it to compare codecs, assess a WAN circuit, or document a conservative bandwidth allowance before deployment.
Calculator
Planning inputsFormula
Per-call rate = codec rate × (1 + packet overhead). Required each way = calls × per-call rate × (1 + signaling) ÷ (1 − reserve).
What the result means
The main result is the provisioned bandwidth required in each network direction. Voice conversations send and receive at the same time, so both upload and download must meet it.
Actual packet overhead depends on codec, packetization interval, IP version, encryption, and tunnel headers. Measure or obtain a vendor value when available.
Example calculation
For 80 calls at 64 kbps with 35% packet overhead, 5% signaling, and a 20% reserve, provisioned demand is 9.07 Mbps each way.
Tips for better results
- Use busy-hour concurrent calls, not extension count.
- Include VPN or SRTP overhead in the packet allowance.
- Verify upstream bandwidth separately.
- Prioritize voice with QoS after capacity is adequate.
- Retest after changing packetization interval or codec.
Frequently asked questions
Why is bandwidth shown for each direction?
VoIP is bidirectional. The upload and download paths each carry a media stream and must independently meet the requirement.
Is codec bitrate the same as on-the-wire bitrate?
No. IP, UDP, RTP, encryption, and link headers increase the transmitted rate above the codec payload rate.
Should I use total phones or concurrent calls?
Use simultaneous active calls during the busy hour. Idle registered phones mainly contribute signaling, not continuous media traffic.
Does silence suppression reduce the requirement?
It can reduce average traffic, but conservative capacity planning often assumes continuous media unless validated data supports a lower factor.
Does adequate bandwidth guarantee good call quality?
No. Packet loss, jitter, latency, queue management, and Wi-Fi conditions also affect voice quality.
Related calculators
VoIP sizing variables
| Variable | Planning use |
|---|---|
| Concurrent calls | Busy-hour simultaneous media sessions |
| Codec rate | Audio payload bitrate |
| Packet overhead | Headers and encapsulation above payload |
| Reserve | Unallocated capacity for variation and growth |