Enterprises searching for "Direct Routing per minute" and "Direct Routing per line" pricing usually find two contradictory answers: vendors quoting pennies per minute, and consultants quoting total-cost models that show 70%+ savings over Calling Plans. Both are true — because Direct Routing pricing has three separate layers, and understanding how they stack is what turns a cheap headline rate into a predictable bill.
This article breaks down all three layers, with real numbers and a worked example.
Layer 1: The License (Fixed, per User)
Teams Phone Standard — currently $8/user/month — is required for Direct Routing, exactly as it is for Calling Plans. This cost is identical across all connectivity options, so it belongs in every model but differentiates none of them. Your per-user voice budget starts at $8; everything after this is where the options diverge.
Layer 2: The SBC (One-Time + Support)
Your Session Border Controller is the fixed infrastructure layer:
- Virtual SBC licensing (AudioCodes, Ribbon, anynode): typically $5,000–$15,000 one-time
- Annual vendor support: typically 15–20% of license cost
- Amortized over three years: roughly $150–$600/month — flat, regardless of user count
This is why Direct Routing gets cheaper per user as you grow: the SBC cost is shared across the whole tenant. See the certified SBC list for which vendors fit which size of deployment.
Layer 3: The SIP Trunk — Where "per Minute" and "per Line" Live
This is the layer the searches are about. Carriers offer two trunking models:
Per-minute metered — you pay for each minute, typically with a monthly per-channel (concurrent call) commitment. US domestic rates typically run $0.0035–$0.01/minute depending on volume and carrier; international varies widely by destination. An average enterprise user makes around 100–200 minutes of calls per month, so per-minute metering is very predictable — until someone discovers international dialing.
Per-line (per-channel) flat — you pay a fixed monthly fee per concurrent call path, typically $0.50–$1.50/path/month, with unlimited or generous usage. The trap is sizing: buy too few paths and callers get busy signals during peaks; buy too many and you're paying for silence.
Sizing Trunks the Right Way
SIP channels are shared, not per-user. For general office voice, a ratio of roughly 20–25 users per concurrent path is safe; call-heavy roles (customer support, trading floors, dispatch) need tighter ratios. A 5,000-user enterprise with office-worker profiles typically needs only ~200 paths.
The 5,000-User Worked Example
- Teams Phone Standard: $8 × 5,000 × 12 = $480,000/year (identical under Calling Plans)
- SIP trunking, 200 paths at ~$1/path/month: $2,400/year
- SBC licensing, amortized + support: ~$4,000/year
- Direct Routing total on top of the license: ~$6,400/year
Compare that to a Domestic Calling Plan at $12/user/month — $720,000/year for the same 5,000 users — and you can see why the Direct Routing savings conversation is so consistent. Full side-by-side in Direct Routing vs Calling Plans and Calling Plan cost optimization.
The Fees That Break Headline Rates
When a carrier quotes you a per-minute or per-line rate, ask these six questions before you compare:
- Rounding increment — 6-second billing (6/60) vs 1-minute rounding can double small-call costs
- Surcharges and regulatory fees — USF contributions and regulatory recovery fees stack on the headline rate
- E911 service — per-user emergency-calling fees and whether location delivery (PIDF-LO) to your PSAPs is supported or bolted on
- DID rental — typically $0.50–$1/number/month across your inventory
- Channel minimums — the smallest trunk you can buy; oversized minimums erase savings for small sites
- Toll-fraud liability — who eats the cost when your SBC is compromised and calls premium-rate destinations at 3 AM
"Cheapest Direct Routing Provider" Is the Wrong Question
The cheapest per-minute rate in the US market loses its advantage the moment rounding, surcharges, and fraud exposure are priced in. What matters is a certified-carrier trunk with honest billing, E911 done properly, and an SBC that prevents toll fraud rather than merely surviving it. The total stack — not the headline rate — is what you should compare.
Want the numbers for your own user count and call profile? Run them through our ROI calculator or talk to us about your voice cost base.