SIP trunk pricing comes down to five parts: per-minute rates, per-channel fees, DID fees, platform fees, and pass-through taxes. SIPNEX’s published US outbound bands run from $0.025–$0.030 per minute under 100,000 minutes a month to as low as $0.005 at 10 million or more. The billing increment moves your real cost as much as the rate does. Everything else is fee structure.
Many SIP trunk providers put their pricing behind a “Contact Sales” button. That makes comparison slow: you need a quote from each vendor, each in its own format, before you can line them up.
SIPNEX publishes its rates because we are a direct carrier that sets its own prices, not a reseller marking up another carrier’s rate card. This guide breaks SIP trunk pricing into its parts so you can compare any provider — including us — like for like.
SIP trunk cost in plain terms
SIP trunk cost varies depending on three things: how many minutes you send, how the carrier rounds each call, and which fees sit on top of the rate. Here is the short version.
- SIP trunking works by carrying your calls over your internet connection instead of copper lines. That is why it can replace traditional phone lines at a lower cost.
- For an outbound call center, most of the bill is outbound calls. The outbound per-minute rate matters most.
- The billing increment can add a third to your bill on short calls.
- Per-channel, platform, and porting fees are the hidden part of the price.
- SIP trunking services price the trunk, not your phone system: a PBX or a dialer can sit behind the same trunk. What moves the rate is your traffic profile — volume, destination mix, and average call length.
The components of SIP trunk pricing
SIP trunk pricing has five components. Some providers bundle them. Some itemize them. Some hide the costly ones in the contract terms. Here is what to look for.
Per-minute rates. This is the core cost: what you pay for each minute of connected call time. Rates vary by direction (outbound or inbound), by destination (domestic or international, metro or rural), and by volume commitment. On SIPNEX’s published rate card, US domestic outbound runs from $0.025–$0.030 a minute under 100,000 minutes a month to as low as $0.005 at 10 million or more. Ask for inbound pricing separately. International rates swing widely by destination, so price each country you actually call.
Per-channel fees. Some providers charge a monthly fee for each concurrent call channel, a model carried over from PRI pricing. It scales with your peak: if your predictive dialer needs 200 concurrent channels, every dollar of per-channel fee adds $200 a month on top of usage. SIPNEX does not charge per-channel fees, and channels are unlimited. Calls per second (CPS) is a separate limit, so get your CPS ceiling in writing.
DID fees. Monthly charges for phone numbers, usually priced separately for local and toll-free. Some providers add a one-time setup fee per DID. Some charge for DID features, such as CNAM registration or E911, that others include. SIPNEX charges a flat monthly fee per DID and includes CNAM registration and A-level STIR/SHAKEN attestation with every DID.
Platform or trunk fees. Some providers charge a monthly trunk fee or a platform access fee. It is a subscription charge on top of usage. SIPNEX does not charge a platform or trunk fee.
Regulatory and compliance fees. USF (Universal Service Fund) contribution, E911 fees, and state and local telecom taxes. Providers pass these charges through in one of two ways: itemized on the invoice, or folded into the per-minute rate. Itemized is more open. Bundled is simpler, but it hides the real per-minute rate.
The billing increment trap
Billing increments decide how each call is rounded before it is priced. The gap between methods is larger than most operators realize.
6-second billing (6/6). A 47-second call bills as 48 seconds (8 six-second blocks). At SIPNEX it is a qualified tier rather than the default: it applies to traffic averaging about 15 seconds ALOC or longer.
12-second minimum with 6-second increments (12/6). SIPNEX’s standard for dialer traffic. A 10-second call bills as 12 seconds. A 47-second call still bills as 48. The short minimum barely moves the math on normal traffic. It keeps ultra-short-call abuse priced honestly.
1-minute billing (1/1). Common with retail and some CPaaS providers. A 47-second call bills as 60 seconds — a full minute. A 61-second call bills as 120 seconds — two full minutes.
1-minute minimum with 6-second increments (1/6). A 47-second call bills as 60 seconds (the 1-minute minimum). A 67-second call bills as 72 seconds (the minimum plus 2 six-second blocks).
Here is the impact at scale. Take a campaign where the average call lasts 45 seconds. That is common in predictive dialing with high AMD rates. On 1-minute billing, each of those calls bills as 60 seconds — a third more than the talk time. On 6-second billing it bills as 48. On 100,000 minutes of talk time at $0.01/minute, that extra third is about $330 a month in waste.
Always ask about billing increments. Then do the math with your own average call duration. Ask again at renewal, because the industry is drifting toward 60/60 on quality routes.
Volume tier pricing
Most carriers lower the per-minute rate as monthly volume rises. These are SIPNEX’s published US outbound bands, as listed on our rate card in September 2026:
| Monthly minutes | SIPNEX published rate | Tier |
|---|---|---|
| Under 100,000 | $0.025 – $0.030 | Starter |
| 100,000 – 500,000 | $0.018 – $0.025 | Growth |
| 500,000 – 1,000,000 | $0.012 – $0.018 | Scale |
| 1,000,000 – 5,000,000 | $0.008 – $0.012 | Volume |
| 5,000,000 – 10,000,000 | $0.006 – $0.008 | Enterprise |
| 10,000,000+ | As low as $0.005 | Carrier |
Rates fall with volume because the carrier’s fixed costs — support, infrastructure, compliance — spread across more minutes. The spread inside a band reflects destination mix: metro minutes cost less to terminate than rural ones. The spread is real money at scale. At the Volume tier, the gap between $0.008 and $0.012 is $4,000 per million minutes.
The published band is a ceiling: clean traffic profiles are quoted below it against actual CDRs. A 6- or 12-month commitment can also lock in a lower tier than your current traffic qualifies for.
The hidden costs
Number porting fees. Some carriers charge a per-number fee to port numbers in. SIPNEX charges no port-in or port-out fees for US numbers.
Contract termination fees. Some carriers lock you into 12- to 36-month contracts with early termination penalties. Read the contract. If there is a term commitment, know the penalty for leaving early. SIPNEX’s standard agreement is month-to-month, with 30 days’ notice to cancel.
Overage penalties. Some carriers tie low per-minute rates to minimum volume commitments. Use less than the minimum and you pay the minimum anyway. That is a take-or-pay contract. Fine if your volume is steady. Risky if it swings.
Support tier charges. Some carriers charge extra for “premium” support: faster response, a dedicated account manager, 24/7 access. On SIPNEX, VICIdial configuration support is included with every trunk. No upgraded support tier required.
Cheap SIP trunks: what low rates actually cost
A cheap SIP trunk is usually a cheap route, and the route is where your savings leak back out. (A free SIP trunk is a trial or a sandbox, never production outbound.) Rates advertised well below the wholesale floor are often built on heavily resold least cost routing. Your calls go to whichever middle carrier is cheapest this week.
The bill for that arrives later. ASR can drop, because marginal routes fail more attempts. And your calls may arrive with B-level attestation or lower. Under the SHAKEN standard (ATIS-1000074), A-level attestation requires the originating provider to know the customer and to have verified its right to the calling number. A carrier that signs calls for a reseller’s customers, several hops from the business placing them, often cannot meet those conditions. Analytics engines treat partial (B) attestation as a lower-trust signal.
Reading a cheap rate deck takes three checks.
Billing increments first. A $0.009 rate on 1-minute billing costs more per call than $0.010 on 6-second billing once your average call runs 45 seconds. Convert every rate to your real average duration before comparing.
Omitted fees second. Per-channel, platform, and porting charges become an effective per-minute surcharge at your real usage. Add them in before the rates are comparable.
Quote-gated tiers third. If the advertised rate needs a volume commitment you do not have, the published number is marketing. Your real rate is whatever sales quotes you.
The extreme end of cheap is “free,” and the same economics apply. What a free SIP trunk actually includes is a $0 account or an in-network tier. It is never free outbound PSTN minutes, because interconnection fees make that impossible to sustain.
Cheap is fine for some traffic. Office-to-office calls, dev and test trunks, and low-volume notification traffic — where a failed attempt costs nothing — do fine on a bargain route. But if you buy in volume, cheap should mean wholesale tiers from a direct carrier. The rate drops because your volume earns it, not because the route quality did.
The same three checks apply double to quote-only vendors: the small wholesalers with no published rates at all. The questions to put to them are in our seven questions to ask your SIP trunk provider.
How to compare providers
To compare SIP trunk pricing, turn everything into a total monthly cost based on your real usage:
- Estimate your monthly minutes (outbound + inbound)
- Estimate your peak concurrent channels
- Count your DIDs (local + toll-free)
- Calculate: (minutes × per-minute rate) + (channels × per-channel fee) + (DIDs × monthly DID fee) + trunk/platform fees + porting fees (amortized)
- Adjust for billing increment (at a 45-second average call, multiply talk minutes by 1.33 for 1-minute billing or 1.07 for 6-second billing)
- Add regulatory fees and taxes, using each provider’s itemized pass-throughs for your traffic
Run this for every provider on your list. The lowest per-minute rate is not always the lowest total cost. Per-channel fees, platform charges, and billing increments can flip the ranking.
Frequently asked questions
What is a fair price for SIP trunking?
Judge the structure before the rate. Look for no per-channel fees, no platform or trunk fees, no setup fees, and no long-term contract requirement. Billing should use short increments: SIPNEX bills dialer traffic 12/6, with 6/6 for traffic averaging about 15 seconds ALOC or longer. For the rate itself, SIPNEX’s published US outbound bands run from $0.025–$0.030 a minute under 100,000 minutes a month to as low as $0.005 at 10 million or more. Convert any quote to cost per connected minute on your real traffic, then compare it against published bands like these. If a quote lands far above them, or the fee list keeps growing, keep asking questions.
Why do some SIP providers hide their pricing?
Reasons vary, and a quote-only model is not proof of a bad deal. Wholesale cost depends on the traffic profile — volume, destination mix, average call length, and short-call ratio — so some carriers price every account individually. The cost to you is time: each quote arrives in its own format, and the fees that change the ranking may not be on it. Ask every provider for the per-minute rate, the billing increment, and the full fee list in writing. Then convert each quote to cost per connected minute on your real traffic before you compare. SIPNEX publishes its tier bands on the rate card and quotes clean traffic below them against actual CDRs.
Should I choose the cheapest SIP trunk provider?
No. The cheapest per-minute rate often comes with tradeoffs that cost more than it saves. Per-channel fees add up at high concurrency. On calls averaging 45 seconds, 1-minute billing charges for a third more time than you used. B-level STIR/SHAKEN attestation is treated by analytics engines as a lower-trust signal. Limited support costs you time when problems arise. Channel caps throttle your predictive dialer. Weigh total cost (all fees plus billing increment effects), attestation level, channel policy, support quality, and reliability. The right pick is the lowest total cost with A-level attestation and unlimited channels — not the lowest per-minute rate on its own.
Does SIPNEX charge per concurrent channel?
No. SIPNEX SIP trunks have unlimited concurrent channels and no per-channel fee. You pay per minute for connected usage and a flat monthly fee per DID. There are no channel fees, platform fees, trunk fees, or setup fees, and no porting fees on US numbers. Unlimited channels does not mean unlimited call attempts: calls per second (CPS) is a separate limit, so confirm your CPS ceiling in writing before a large campaign. Unlimited channels suit predictive dialing, where channel demand bursts as answer rates swing.
SIPNEX publishes its rates because we are the carrier setting the price. No per-channel fees. No platform fees. 12/6 billing, with 6/6 for traffic averaging about 15 seconds ALOC or longer. A-level STIR/SHAKEN attestation. That is what a cheap SIP trunk should mean: a low effective cost per connected minute, not a low headline rate. See the rate card.
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