A single VoIP call uses roughly 90 Kbps in each direction with the standard G.711 codec, and less with compressed codecs. For a small office, that means a typical business internet plan has far more bandwidth than your phones need. What decides call quality is usually not the size of the pipe. It is how steady the connection is and whether other traffic crowds your calls out.
This guide shows you how to size bandwidth for your own office, what else your network has to deliver, and how to check that it does.
TL;DR
- Plan on about 90 to 100 Kbps per simultaneous call, in both directions. Count concurrent calls, not employees.
- Add roughly 20% headroom, then add whatever your computers, cameras and cloud apps use on top.
- Upload speed matters as much as download. Cable and DSL plans often have a small upload side, and that is where phones run out first.
- Latency, jitter and packet loss break calls more often than a lack of Mbps. Prioritize voice traffic on your router.
- Test with a real VoIP test at your busiest hour, not just a speed test.
Table of Contents
- How much bandwidth one VoIP call uses
- What the FCC says about internet speed for VoIP
- How to calculate bandwidth for your office
- Upload and download both count
- Network requirements beyond bandwidth
- How much extra bandwidth to reserve
- Our perspective: bandwidth is rarely the problem
- How to test whether your network is ready
- Picking internet service for VoIP
- What this means for cost
- FAQ
- Sources
How much bandwidth one VoIP call uses
Bandwidth per call depends on the codec, which is the method that turns your voice into data, and on the packet overhead wrapped around it.
The codec figure is only the voice payload. TechTarget explains that G.711 uses 64 Kbps and G.729 uses 8 Kbps, and that IP overhead adds about 23 Kbps in its example, which lands a G.711 call near 87 Kbps. An Ingate application note arrives at the same place by counting headers: a G.711 call with 20 ms packets needs approximately 85.6 Kbps one way, which it rounds to about 90 Kbps.
Two things move that number:
- Codec. G.711 is uncompressed, widely supported and sounds good. G.729 is far lighter on the wire but compresses audio more and usually adds licensing or compatibility questions.
- Packet size. Ingate notes that sampling more often adds network overhead. Shorter packets mean more headers for the same amount of speech.
A practical rule: budget 100 Kbps per call in each direction. It is slightly generous for G.711, and it leaves room for the signaling traffic that sets up and ends calls.
Why "per call" beats "per user"
You only use bandwidth while someone is on the phone. A 30-person office rarely has 30 people talking at once. A receptionist-heavy dental office or a hotel front desk may peak at 6 to 10 calls. A call center is different, and may run nearly every seat at once.
Look at your busiest hour. If you have an existing phone system, its call logs show how many calls overlapped. If you do not, count your lines and your realistic worst case, such as a Monday morning or a promotion day.
What the FCC says about internet speed for VoIP
The FCC's Broadband Speed Guide lists VoIP calls at less than 0.5 Mbps of download speed. The same guide describes its figures as rough guidelines and assumes one activity at a time.
That second point is the one that matters at work. A phone call on a quiet line needs very little. A phone call while four people stream video, a laptop backs up to the cloud and a cash register syncs sales is a different situation. The FCC number tells you VoIP is light. It does not tell you your office is quiet.
How to calculate bandwidth for your office
Use this formula:
Total bandwidth = (bandwidth per call × peak concurrent calls) + other traffic, then add about 20%
Here it is in four steps.
- Count peak concurrent calls. Check call logs or estimate your worst-case hour.
- Multiply by 100 Kbps. This gives the voice load, and it applies to upload and download separately.
- Add other traffic. Video meetings, file sync, cloud software, guest Wi-Fi and security cameras all share the same connection.
- Add roughly 20% headroom. This is our working rule for retransmissions and spikes, not a standard.
Worked examples
| Office | Peak concurrent calls | Voice load (each direction) | With 20% headroom |
|---|---|---|---|
| Home office, 1 to 2 lines | 2 | 0.2 Mbps | 0.24 Mbps |
| Small business, 10 staff | 5 | 0.5 Mbps | 0.6 Mbps |
| Medical or dental office | 10 | 1.0 Mbps | 1.2 Mbps |
| Small hotel front desk and rooms | 15 | 1.5 Mbps | 1.8 Mbps |
| Busy school office with classroom phones | 25 | 2.5 Mbps | 3.0 Mbps |
These are voice-only figures. Add your other traffic on top. If your 10-staff office also runs three video meetings at once, plan the video separately and add it to the 0.6 Mbps for phones.
The pattern is clear: even 25 simultaneous calls fit in a few megabits. Most business connections have room. The risk is not the size of the plan. It is sharing the plan with traffic that does not play nicely.
Upload and download both count
Voice flows both ways at the same time. Every call sends your voice up and receives the caller's voice down, so a call uses about the same amount of bandwidth in each direction.
This catches people out because many plans are asymmetrical. A cable plan may advertise a large download number and a much smaller upload number. If you have 10 concurrent calls (about 1 Mbps up) and also upload large files or run video meetings, your upload side can saturate long before download does. When that happens, callers hear choppy audio on your end.
When you compare internet plans, read the upload number first. Fiber and business-class plans with symmetrical speeds make this problem mostly disappear.
Network requirements beyond bandwidth
Bandwidth is the easy part. Three measurements decide whether a call sounds clear.
Latency
Latency is the time voice takes to get from one end to the other. According to VoIP-Info, callers usually notice voice delays of 250 ms or more round trip, and ITU-T G.114 recommends a maximum of 150 ms one way. That figure covers the whole path, including the part you do not control, so your own network should contribute very little.
Jitter
Jitter is variation in delay. Packets that arrive unevenly make speech sound robotic or clipped. Phones use a jitter buffer to smooth this out, but as the same VoIP-Info page notes, quoting Cisco, buffers add delay and only help with variations under about 100 ms. The fix is a steady connection, not a bigger buffer.
Packet loss
Voice is not forgiving of lost packets. VoIP-Info reports that even 1% packet loss can significantly degrade a G.711 call, and more compressed codecs tolerate even less. This is why a connection that tests fast can still produce bad calls: speed tests do not penalize loss the way a live conversation does.
Quality of service (QoS)
QoS tells your router which traffic goes first. On business routers you typically mark voice media with the DiffServ "Expedited Forwarding" class. Wikipedia's overview of Differentiated Services describes EF as suited to voice and video, and often given strict priority queuing.
A few practical points:
- Prioritization only helps at the point where traffic queues up, which is almost always your router's internet-facing port. Setting it on a switch alone does little.
- Putting phones on their own voice VLAN keeps them away from laptops and guest devices. This guide to VLAN and PoE switch basics covers the same network building blocks, which apply to desk phones as well.
- Wi-Fi phones and softphones on busy wireless networks are the usual source of jitter. Wired desk phones avoid that.
- Consumer routers with "gaming" or "smart" QoS are inconsistent. A router you can configure and monitor is worth the small extra cost.
How much extra bandwidth to reserve
Voice is small, so the safe approach is to protect it rather than oversize everything.
- Reserve for voice, then cap the rest. Priority queuing guarantees phones their slice even when someone starts a large upload.
- Plan 20% over your voice peak. It covers bursts and signaling.
- Count video separately. A single HD video meeting can use many times the bandwidth of a phone call. If your team lives in video meetings, size for those first.
- Think about growth. Adding staff, a second location or guest Wi-Fi changes the load. Revisit the numbers once a year.
If a link is shared with a heavy user, such as a guest network at a hotel, put guest traffic on a separate, rate-limited segment so a streaming guest cannot affect the front desk.
Our perspective: bandwidth is rarely the problem
We set up and manage business phone systems for small businesses, non-profits, schools and hotels, and the pattern is consistent. When a customer reports bad calls, the first suspect is almost always "not enough internet". More often the cause is something else on the same network: a consumer router, a Wi-Fi phone in a weak spot, a large backup running at noon, or an internet connection with a thin upload side.
That is why our setup does not stop at the phones. We configure the system, pre-configure the desk phones, and monitor the network proactively through our Network Operations Center, so problems show up before your callers notice. Support is 24/7 and handled by real people, and system changes and support calls are handled the same day.
Our advice for any small business is to size bandwidth with the simple formula above, buy a plan with a decent upload side, put voice first on your router and test at your busiest hour. Do those four things and a typical office will not need a premium internet plan for phones.
— User
How to test whether your network is ready
A standard speed test shows download and upload speeds. It does not show whether your line is steady. Do both.
- Run a speed test at a normal busy time, and note upload as well as download.
- Run a VoIP-specific test. Tools such as the Visualware VoIP assessment place simulated call traffic on your connection and report jitter, packet loss, latency and a call quality score. Choose the number of concurrent calls to match your peak.
- Run a sustained ping to a reliable address for a few minutes and look at the spread between minimum and maximum response times. A wide spread signals jitter.
- Test wired and wireless separately. If wired is clean and Wi-Fi is not, move phones to Ethernet or fix coverage.
- Repeat during a heavy period, such as a big upload or a video meeting, to see how the phones behave under load.
Common symptoms and what they usually mean
| What you hear | Likely cause | First thing to try |
|---|---|---|
| Choppy or robotic voice | Jitter or packet loss | Check Wi-Fi, run a VoIP test, enable QoS |
| One-way audio | Firewall or NAT settings | Review firewall rules with your provider |
| Echo or talk-over | High latency | Check the connection path and any VPN |
| Quality drops at certain times | Competing traffic | Cap backups and streaming, prioritize voice |
| Calls drop after a few minutes | Unstable connection or router | Test for packet loss, update or replace the router |
If you keep seeing problems after the basics, a managed provider can look at the network with you. That is the point of having monitoring built into the service rather than handled after the fact.
Picking internet service for VoIP
For most small offices, the checklist is short:
- Symmetrical or generous upload. Fiber is ideal. Cable works for light use if the upload side is adequate for your calls plus everything else.
- A business-class plan if calls are central to revenue. These often come with better support and faster repair.
- A backup connection for operations that cannot go quiet, such as a hotel front desk or a clinic. A cellular failover is a common, inexpensive option.
- A router you can manage, with QoS, VLAN support and logs.
- Wired phones where you can. Use Wi-Fi for laptops and mobile apps.
If you are still deciding on a provider, our guides to choosing VoIP for a small business and the key features a small business system should have cover what to compare.
What this means for cost
Because bandwidth needs are modest, the real cost of VoIP is the service itself. Many providers charge per user, so every new hire raises the bill. Our approach is a flat rate: the Business plan starts at $125 per month with unlimited users and no per-user fees, and the Home Office plan is $25 per month. Setup is included at no charge, and there are no contracts. You can see the details on our pricing page, and our guide to what a business phone system costs walks through the other line items to watch.
Hotels and motels have their own needs, such as guest-room phones and a busy front desk. Our hotel phone systems start from $125 per month per property.
FAQ
How much bandwidth do I need for 10 VoIP calls?
About 1 Mbps in each direction for voice alone, based on 100 Kbps per call. Add around 20% headroom, which brings you near 1.2 Mbps, and then add whatever your other devices use. Remember that this is concurrent calls, not 10 employees.
What internet speed do I need for VoIP?
VoIP itself is light. The FCC's guidance lists less than 0.5 Mbps of download for a call on its own, and it treats that as a rough guideline. For an office, work from your peak concurrent calls and your other traffic, and check that upload speed is adequate.
Does VoIP use more bandwidth than a regular phone call on a mobile network?
The amounts are small either way. A call on G.711 uses about 90 Kbps in each direction, which a normal broadband or Wi-Fi connection handles easily. The difference is that VoIP shares your internet connection with everything else, so steadiness matters more than size.
Do I need QoS for VoIP?
On a quiet network with a few phones, you may get by without it. As soon as backups, video meetings or guest Wi-Fi share the connection, prioritizing voice at the router protects your calls. It is a small setting that prevents the most common complaints.
How can I monitor VoIP call quality?
Run a VoIP-specific test at your busiest hour and watch jitter, packet loss and latency rather than speed alone. Ongoing monitoring catches problems that appear only at certain times. With our service, proactive network monitoring is part of the managed setup.
Sources
- Broadband Speed Guide, Federal Communications Commission
- Application Note on VoIP bandwidth, Ingate Systems
- Calculating VoIP bandwidth needs for SIP trunk services, TechTarget
- QoS for VoIP implementations, VoIP-Info
- Differentiated services, Wikipedia
- VoIP assessment test, Visualware
- IP video intercoms: PoE, VLAN and support, Vuetek Systems