SIP trunks connect your PBX, SBC, or contact center to the PSTN over IP. US buyers shop here when they already own call control—FreePBX, Cisco, Teams Direct Routing, or BYOC CCaaS—and want elastic capacity without PRI hardware.
Score concurrency/burst, STIR/SHAKEN and reputation tooling, number inventory, failover/POPs, emergency calling, and APIs. Transparent per-minute rates help; FOC porting and outage support often decide renewals.
Fit map: Bandwidth, Inteliquent/Sinch, Peerless, and VoIP Innovations for carrier/enterprise interconnect; Telnyx, Twilio Elastic SIP, Plivo, SignalWire, and Vonage for developers; Flowroute and VoIP.ms for DIY PBX operators.
If nobody on staff can read a SIP trace, buy UCaaS on /compare instead. Otherwise shortlist below and model minutes with the SIP trunk calculator.
Browse 12 providers
Filter by team size or budget. Each card includes starting price (or Custom when list pricing is unpublished), highlights, pros and cons, and a full profile drawer.
Telnyx
Private backbone performance
★
4.4 (scores from published listings)
Starting price
Usage
pay-as-you-go
Best for
High-volume API voice/SMS
Owns their own private fiber network for better quality and lower cost.
By the Telecom Audit Advisory BoardUpdated August 5, 2026
Quick picks
Telnyx: Transparent pricing and private-network SIP for technical teams.
Bandwidth: US number scale and enterprise/platform interconnect.
Twilio Elastic SIP: Elastic capacity inside a broad CPaaS ecosystem.
VoIP.ms: Budget DIY trunks for FreePBX-class operators.
Pricing caveats
SIP is usually usage-priced (minutes, numbers, features)—published rates help, but enterprise agreements still exist. Model busy-hour concurrency, toll-free, and domestic vs international separately. UCaaS seats are the wrong comparison unit.
Published plan pricing
These figures are verified by our editorial team. Prices below reflect the plans we track, not introductory marketing rates. Always confirm taxes, regulatory recovery fees, and add-ons on the quote.
Provider
Starting Price
Plans on File
Telnyx
Usage pay-as-you-go
SIP Trunking: 0.005/per min
VoIP.ms
$0.85 /DID/mo
Self-Managed: 0.85/per DID
Bandwidth
Usage per minute / number
Usage / Custom: Custom
Twilio Elastic SIP
Usage per minute
Usage / Custom: Custom
Flowroute
Usage per minute
Usage / Custom: Custom
Plivo
Usage per minute
Usage / Custom: Custom
Inteliquent (Sinch)
Custom wholesale / enterprise
Usage / Custom: Custom
IntelePeer
Custom platform quote
Usage / Custom: Custom
Peerless Network
Custom carrier quote
Usage / Custom: Custom
SignalWire
Usage per minute / resource
Usage / Custom: Custom
Vonage API SIP
Usage per minute
Usage / Custom: Custom
VoIP Innovations
Custom wholesale quote
Usage / Custom: Custom
Scenario verdicts
Your situation
Start here
Why
Microsoft Teams Direct Routing
Bandwidth
Enterprise interconnect
US numbers
Operator maturity
Startup building voice features
Telnyx
API ergonomics
Usage clarity
Voice AI adjacency
Wholesale / multi-tenant provider
VoIP Innovations
Wholesale motion
Provider tooling
SIP at scale
FreeSWITCH-centric architecture
SignalWire
FreeSWITCH DNA
Programmable control
Flexible media
Five capabilities that change buying outcomes
Pressure-test these on your shortlist—what each capability does, and the buyer outcome it unlocks.
Concurrent call capacity & burst behavior
Trunks are limited by licensed or elastic concurrent channels. Spikes—storms, outages, campaigns—need headroom or automatic burst without mystery failures.
Buyer outcome: size to busy-hour erlang, not average daily minutes. Ask how sudden concurrency is handled before calls fail.
STIR/SHAKEN & outbound reputation
US outbound fails when attestation and reputation are weak. Providers differ on SHAKEN, CNAM, and remediation when carriers flag traffic.
Buyer outcome: require a clear reputation workflow before migrating outbound campaigns.
Number inventory & porting operations
Local/toll-free inventory and fast porting often beat a fractional minute discount. Platforms that also sell numbers simplify architecture.
Buyer outcome: faster market expansion. Score FOC timelines with references, not aspirational SLAs.
SBC interoperability & codec policy
Your SBC/PBX must interoperate: TLS/SRTP, codecs, and SIP header quirks. Cheap trunks that break transfers are not cheap.
Buyer outcome: lab-test hold/transfer/conference (and fax if needed) before cutover.
Failover, POPs, and emergency calling
Dual registration, DNS failover, and multi-POP designs keep sites online. Confirm E911 models for remote users.
Buyer outcome: treat uptime as architecture. Get diagrams and a clear split of carrier vs your responsibilities.
Frequently asked questions
Do I need SIP trunks or a full UCaaS platform?
Buy SIP trunks when you already operate a PBX/SBC/CCaaS and have staff who can manage dial plans, certificates, and QoS. Buy UCaaS when you want apps, devices, and vendor support as a package.
Hybrid models exist—Teams Phone with Direct Routing, or CCaaS with BYOC trunks—but they raise architectural complexity.
If your team cannot troubleshoot one-way audio, start with UCaaS on /compare.
How should I compare per-minute pricing?
Normalize to your traffic mix: local, long distance, toll-free inbound, international, and short-duration call setup fees. Include number rental and feature charges.
The cheapest rate deck loses if ASR (answer-seize ratio) is poor or support is unreachable during an outage.
Use the SIP trunk calculator with real CDRs, not marketing averages.
What is BYOC?
Bring Your Own Carrier means a UCaaS or CCaaS platform uses your SIP trunks instead of the vendor's PSTN. It can reduce minutes cost or meet sovereignty needs.
BYOC shifts more responsibility to you for quality and compliance. Confirm the platform's certified carriers and SBC requirements.
It is powerful for sophisticated IT; it is risky for first-time VoIP buyers.
How many providers should I dual-home?
Many enterprises dual-home critical sites across two SIP carriers or POPs for resilience. SMBs often start with one provider plus careful failover to a backup route.
Dual-homing doubles operational surface area—dial plan discipline matters. Document primary/secondary behavior for each site.
Test failover quarterly; paper designs drift.
Can SIP trunks support remote workers?
Yes, via SBC/VPN/VDI architectures or WebRTC edge, but remote work often pushes buyers toward UCaaS softphones with vendor-managed E911 prompts.
If you keep SIP, invest in identity-aware access and dynamic emergency locations. Do not expose a PBX directly to the internet without an SBC.
Remote-heavy firms should re-read UCaaS options before over-investing in DIY SIP.
What security controls are non-negotiable?
TLS/SRTP where supported, strong SIP authentication, ACL/SBC policies, fraud alerting, and least-privilege portal access. International dialing locks prevent toll fraud.
Ask providers how they detect traffic anomalies and how fast they can block compromised endpoints.
Security is shared responsibility—carriers cannot save a misconfigured open PBX alone.
How do APIs change the SIP buying decision?
API-first carriers let you automate number orders, call control, and troubleshooting data. That matters for platforms and multi-tenant operators more than for a single office PBX.
If you will never script against an API, prioritize support quality and portal clarity over developer prestige.
Telnyx/Twilio/SignalWire-class buyers should still validate PSTN basics—API polish does not fix bad QoS.
What should a SIP pilot include?
A production-like codec set, hold/transfer tests, busy-hour load, failover drill, number port of a non-critical block, and emergency call test procedures where allowed.
Capture MOS/RTP stats and a sample of CDRs. Involve the same engineers who will on-call after go-live.
Do not declare victory on a five-call demo from the vendor's office Wi-Fi.
