VoIP Cost Guide
INVITE sip:reader@voipcostguide.com → 200 OK
What VoIP Really Costs — and How to Fix It When It Breaks
VoIP Cost Guide is two libraries in one: honest, model-based breakdowns of what a business phone system costs, and symptom-first troubleshooting guides written the way a VoIP engineer actually works — capture first, theory second.
Latest guides
How to Read a SIP Ladder Diagram
The single most useful VoIP skill: following one call through a capture, message by message.
One-Way Audio: Causes and Fixes
You can hear them, they cannot hear you. Nine times out of ten it is NAT or a blocked RTP range.
VoIP Budget for a 25-User Business
A complete worked budget — seats, phones, numbers, fees and the lines most quotes leave out.
SIP ALG Explained: Why It Breaks Calls
The helpful router feature that rewrites your SIP packets into garbage. When to switch it off.
The Hidden Costs of Business VoIP
DIDs, e911 fees, taxes, hardware and porting — everything that never appears in the headline price.
Choppy Audio and Jitter: A Diagnosis Guide
Robotic, garbled, underwater voices are a network measurement problem. Here is how to measure it.
SIP Trunk Pricing Models Compared
Per-channel, per-minute and unlimited trunks cost very different amounts at the same call volume.
Calls Drop After Exactly 15 or 30 Minutes
A call that dies on a timer is a clue, not a mystery: session timers and UDP timeouts explained.
The two pillars
VoIP Costs
Per-user pricing, hidden fees, SIP trunk models, budgets by business size from 5 to 50 seats, and contact-center costs — with the math shown, not just the marketing number.
Troubleshooting & Fundamentals
One-way audio, choppy calls, echo, registration failures and every common SIP error code — each guide starts from the symptom and works to the root cause.
How a VoIP call works, in one picture
Every guide on this site comes back to the same two conversations. SIP (Session Initiation Protocol, RFC 3261) sets the call up; RTP carries the actual voice. When something breaks, the first question is always: which of the two is failing? A call that never rings is a SIP problem. A call that rings but sounds like a robot is an RTP or network problem. That one distinction solves half of all VoIP tickets before any tool is opened.
# A healthy call, simplified
Phone Proxy/Server Callee
|--- INVITE ------->|--- INVITE ------->|
|<-- 100 Trying ----|<-- 100 Trying ----|
|<-- 180 Ringing ---|<-- 180 Ringing ---|
|<-- 200 OK --------|<-- 200 OK --------|
|--- ACK ---------->|--- ACK ---------->|
|<======= RTP voice both ways =======>|
|--- BYE ---------->|--- BYE ---------->|
|<-- 200 OK --------|<-- 200 OK --------|
New to this? Start with How VoIP Works and How to Read a SIP Ladder Diagram. Shopping for a system? Start with Hosted VoIP Pricing Explained and the 10-user worked budget, or run your own numbers with the Voip cost calculator.
Why trust the numbers here?
Cost guides on this site teach the pricing model — the line items, the fee categories, the formulas — and work examples with clearly labeled sample rates you can replace with any quote in front of you. Where a figure comes from a published source (a regulator fee schedule, a standards document, a provider's public price page), the page names the source and dates it. We never present an invented vendor price as fact, and we take no commissions from the providers discussed. Read more in our methodology.