Per-second vs per-minute billing: what it costs you
How a call is rounded matters as much as the headline per-minute rate. Billing increments quietly shape margin and customer trust, and they deserve as much attention as the rate itself.
Two operators can advertise the same per-minute rate and still charge customers very differently. The difference is the billing increment: the unit of time a call is rounded to before the rate is applied. Rounding every call up to the next whole minute can add up to far more than a small adjustment.
On calling cards, where customers make many short calls and watch their balance closely, the increment is not a back-office detail. It shapes how fair the product feels, how competitive the price looks, and how much margin sits hidden in the rounding.
How billing increments work
A rate deck is more than a price per minute. A few small settings decide how much answered time a customer actually pays for.
First increment
The smallest unit a call is charged on when it connects. A 60/60 deck rounds the whole call up to a full minute, while a 1/1 deck charges from the first second of answered time.
Subsequent increment
The unit used after the first one. A 30/6 deck charges a 30-second initial block, then rounds the rest up in 6-second steps. The two numbers do not have to match.
Minimum charge
A floor applied regardless of duration, so very short answered calls still carry a defined cost. This protects margin on routes with high setup overhead.
Connection or setup fee
A one-off amount added when a call is answered, separate from the per-unit rate. It can make a low headline rate far less competitive than it appears.
Rounding direction
Almost always upward to the next whole increment. The larger the increment, the more rounded-up time a customer pays for across many short calls.
The same call, two increments
The numbers below are a hypothetical example to show the shape of the effect, not market data or a real rate. Take one answered call lasting 75 seconds.
Per-minute (60/60)
The call is rounded up to the next whole minute, so 75 seconds is charged as 2 minutes. The customer pays for 120 seconds.
Per-second (1/1)
The call is charged on the answered time, so 75 seconds is charged as 75 seconds. The customer pays for exactly what they used.
In this illustrative case the per-minute deck bills 45 seconds of time the customer never spent on the call. At the same rate, that gap is pure overcharge created by rounding, and it repeats on every short call.
Where per-minute rounding hurts
Large increments can look harmless on a single call. Across a base of customers making many short calls, the rounding becomes visible, and not in a way that builds trust.
The pattern shows up in three places: customer relationships, competitiveness, and the clarity of the numbers behind the product.
- Disputes and lost trust, because a customer who sees a 75-second call billed as two minutes feels overcharged on a calling card.
- Uncompetitiveness on price-sensitive routes, where a low per-minute rate is undercut once large rounding increments are taken into account.
- Opaque margins, because rounding gains are buried in the increment rather than shown as a clear rate, making decks hard to compare and audit.
- Accurate, fairer charging, where a customer pays for the answered time used rather than for rounded-up minutes they never spent on the call.
- More competitive card pricing, because the headline rate maps closely to what is actually billed and stands up to comparison shopping.
- Different increments per route or rate deck, so a route with high setup cost can carry a sensible minimum while clean routes bill at one-second granularity.
Where per-second helps
Per-second rating does not have to mean giving up margin. It means putting the margin somewhere visible, such as the rate, a minimum charge, or a connection fee, instead of hiding it in rounding.
Seshnova rates calls in real time on A to Z rate decks, so increments, minimum charges, and connection fees can be set per route rather than forced into one global rule.
Increments are a per-route decision
There is no single right increment for every destination. A route with high setup cost may justify a minimum charge or a larger first block, while a clean, high-volume route may bill fairly at one-second granularity. The mistake is treating rounding as one global setting applied everywhere by habit.
The better approach is to decide increments, minimum charges, and connection fees route by route, with real-time per-second rating underneath so the choice is deliberate and the charge is easy to explain to a customer.