Why the billing increment matters as much as the rate
A billing increment is written as initial/recurring seconds: the first number is the minimum billed duration for a connected call, the second is the block calls are rounded up to after that. A cheap per-minute rate on a coarse increment like 60/60 can cost more in practice than a slightly higher rate billed 1/1, if your calls are short — the calculator below shows the real numbers for your own traffic instead of a generic example.
How each increment behaves
| Increment | Meaning | Worst case for a short call |
|---|---|---|
| 1/1 | Every connected second billed individually, no minimum beyond 1 second. | None — always billed exactly. |
| 6/6 | 6-second minimum, then 6-second blocks. | A 1-second call bills as 6 seconds. |
| 20/20 | 20-second minimum, then 20-second blocks. | A 1-second call bills as 20 seconds. |
| 30/6 | 30-second minimum, then 6-second blocks. | A 1-second call bills as 30 seconds. |
| 60/1 | 60-second minimum, then 1-second blocks. | A 1-second call bills as 60 seconds; longer calls bill precisely after the first minute. |
| 60/60 | Full one-minute blocks throughout. | A 61-second call bills as 120 seconds. |
How the calculation works
Given a connected call duration in seconds: if the duration is at or below the initial increment, the call bills as the initial increment; otherwise it bills as the initial increment plus the recurring increment rounded up to cover the rest of the call. Total cost is billed minutes × your advertised per-minute rate. The "effective rate per actual minute talked" below divides that cost by the real (unrounded) minutes — that's the number that lets you fairly compare two offers with different increments.
Where to find your real increment
Published rate sheets list the billing increment alongside the per-minute rate for each destination — see the live VoIP rate comparison for current increments by destination, or request a route test before committing volume.