A truly free SIP trunk covers the account, never the outbound minutes: what’s actually free is a $0-monthly pay-per-use account, a limited-time trial, or in-network calling. No carrier terminates outbound PSTN calls at volume for free, because every call to the public network costs the carrier per-minute interconnection fees.
An account that costs $0 a month is easy to find. A trunk that delivers real outbound calls to the phone network for $0 is not — and the gap between those two sentences is this entire market.
SIPNEX is an FCC-licensed carrier that sells SIP trunking — bias disclosed. Here is the honest map: what free SIP trunking includes, what it’s good for, and where the free-adjacent offers quietly cost you.
What a free SIP trunk actually includes
“Free SIP trunk” is marketed in four distinct shapes. Verified examples, all checked August 2026:
| What’s marketed as “free” | Verified example | What costs $0 | What you still pay for |
|---|---|---|---|
| $0-monthly pay-per-use account | Callcentric Pay Per Call / IP Freedom | The account, voicemail, in-network calls | Per-minute PSTN rates; the phone number |
| Free cloud PBX layer | Zadarma free PBX | PBX features: IVR, transfer, recording | The calling itself; paid plans from $4/user/mo |
| Time-limited trial | Kixie 7-day trial; JustGOcloud 30-day promo | Everything, briefly | Full rates when the clock runs out |
| Open-source software | VICIdial, Asterisk | The software license, every feature | Servers, carrier trunks, every minute |
The cleanest version of free is the $0-monthly account. As of August 2026, Callcentric’s plans page lists its IP Freedom outbound plan at $0.00/month with unlimited calling to other Callcentric customers and other VoIP networks, a Pay Per Call plan at $0.00/month billed at per-minute rates, and free voicemail. Note what’s missing: a phone number. Incoming numbers are paid — a “Dollar Unlimited” DID from $1.00/month (residential only, select US states) or a pay-per-minute DID at $1.95/month plus $0.015/min.
Zadarma inverts the model: the free layer is the PBX, not the trunk. As of August 2026 it advertises a free cloud PBX — IVR, call transfer, call recording, voicemail — plus a free CRM, with paid PBX plans from $4/user/month. Its homepage doesn’t spell out the free tier’s caps or top-up conditions, so read the tariff pages before building on it. Either way, the calls themselves remain metered service.
The third shape is the trial. Kixie runs a 7-day free trial on its per-seat dialer plans; GOautodial’s hosted JustGOcloud advertises a 30-day promo with the first month free for up to 10 agents. Trials are genuinely free — but they’re evaluation windows, not a phone-bill strategy.
The fourth shape confuses the most buyers: open-source software. VICIdial and Asterisk cost nothing to license — that $0 is real and permanent — but software is not carriage. It’s the one version of “free” that holds up, covered below.
Across the providers we checked, none was verified as advertising a permanently free, full SIP trunk with an included phone number. That’s a survey, not proof about every provider on earth — but the pattern is consistent enough to be your planning assumption.
Why outbound calling is never free
Two definitions make the economics obvious. In SIP trunking, origination is the PSTN delivering inbound calls to your systems; termination is your systems placing outbound calls to the PSTN. Termination costs your provider money on every call: per-minute interconnection fees paid to downstream carriers to complete your traffic.
That’s why free offers cluster where they do. Free in-network calling is affordable — the traffic never leaves the provider’s switch — and a trial is marketing spend. Paying interconnection on your outbound volume forever while charging nothing is neither. Any “unlimited free outbound” pitch is capped, in-network only, temporary — or recovering the cost somewhere you can’t see.
What free SIP trunking is genuinely good for
Free tiers earn their keep in the lab: validating a PBX config, testing a softphone, learning SIP signaling, or proving your firewall and NAT behave before any money moves. The settings you validate on a free tier — codecs, registration, DTMF — move unchanged to a production carrier — the sequencing our Asterisk SIP trunk configuration guide recommends.
The line to hold: free tiers validate configuration, not capacity. Answer rates, caller-ID reputation, concurrency, and route quality only reveal themselves under production traffic.
The free-adjacent traps
Three offers sit close enough to “free” to deserve a closer read.
Trials that want a card. A trial with a credit card attached is a subscription with a delay. Before testing, check what happens the day the trial ends — auto-conversion pricing is where the real rate hides.
“Free minutes” bundles. Bundled minutes aren’t free; they’re priced into whatever the bundle is attached to — a seat license, a platform fee, a higher per-minute rate after the allowance. Compare the all-in cost per minute, not the headline.
Grey-market resellers. The most expensive “free” is the unauthorized reseller pushing cut-rate, multi-hop routes. Cheap multi-carrier routing has measurable symptoms: Bandwidth’s glossary notes post-dial delay is more common on wholesale least-cost routing products, because each carrier in the chain takes a few seconds to acknowledge it can complete the call. Caller-ID trust degrades across those chains too — the i3Forum’s Restore Trust initiative exists for exactly that reason. The honest breakdown of direct versus multi-hop routing is in our VoIP routes guide.
What legitimately cheap looks like
Since free outbound doesn’t exist, the real question is what fair looks like. Three markers:
Published per-minute rates. Printed prices are prices you can hold a provider to. SIPNEX publishes its rates; many providers quote only through sales calls.
Dialer-friendly billing increments. The big CPaaS platforms — Twilio and Telnyx among them — bill voice at 60/60, rounding every call up to a full minute. SIPNEX bills dialer traffic 12/6: a 12-second minimum, then 6-second increments, so a 45-second call bills as 48 seconds instead of 60. On short-call outbound traffic, the increment moves the bill more than the rate does.
Transparent number and feature pricing. DIDs, e911, and channel policy priced in the open, not discovered on the first invoice. The full teardown of what SIP trunking should cost — rates, increments, fees, and the comparison math — is in our SIP trunk pricing guide.
The real free stack: VICIdial plus paid carriage
If your search was really about free auto dialer software, the answer has existed for two decades: VICIdial is the free dialer. Open-source under the AGPL, no license cost, full predictive dialing, inbound ACD, and recording included — self-installed on servers you control.
That’s the version of “free” that holds up in production: free software plus paid carriage. The software line genuinely is $0 forever; the carrier line is metered, negotiable, and honest. Free software plus “free” carriage isn’t a stack — it’s a trial. What the $0 license actually costs to run — servers, expertise, telecom, compliance — is mapped line by line in our VICIdial pricing breakdown, and the trunk wiring lives in the VICIdial SIP trunk setup guide.
Frequently asked questions
Does a completely free SIP trunk with a phone number exist?
Not from any provider we could verify as of August 2026. The verified free offerings are narrower: $0-monthly pay-per-use accounts and free in-network calling (Callcentric), a free cloud-PBX layer with metered calling (Zadarma), and time-limited trials (Kixie’s 7 days, JustGOcloud’s 30-day promo). In every case the phone number, the outbound PSTN minutes, or both stay paid. Treat any permanently-free-with-number claim as fine print to read, not a plan to build on.
Why is there no free SIP trunk for outbound calls?
Because termination costs the provider money on every call. When your trunk sends a call to the PSTN, your provider pays downstream carriers per-minute interconnection fees to complete it. In-network calls can be free — they never leave the provider’s switch — and trials can be subsidized briefly. But nobody can absorb interconnection fees on real outbound volume forever while charging nothing. Free outbound at scale isn’t sustainable pricing — it’s a red flag about where the money actually comes from.
What is a free SIP trunk actually good for?
Lab work — and it’s genuinely good at it. A $0 account lets you validate PBX configuration, codecs, registration, DTMF, and firewall behavior before spending anything, and those settings transfer unchanged to a production carrier. What a free tier cannot tell you is how your traffic performs at volume: answer rates, caller-ID reputation, concurrency, and route quality only show up on production trunks. Validate config for free; buy capacity when it’s time to dial.
What should replace a free SIP trunk in production?
A carrier with published per-minute rates, billing increments that fit your traffic, and its own regulatory standing. For dialer traffic, increments matter most: 60/60 rounding punishes short calls, while 12/6 billing charges a 45-second call as 48 seconds. Direct carriers can also sign their own STIR/SHAKEN attestation instead of inheriting a reseller’s. SIPNEX is an FCC-licensed carrier with published rates, 12/6 dialer billing, and A-level attestation signed under our own certificate — the checklist we’d apply to anyone, applied to us.
Free tiers are for the lab. When the traffic is real, the honest math is published rates and dialer-grade increments — see our pricing or call (833) 665-2220.
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