VoIP billing increments explained: 6/6, 60/60, 30/6 and 1/1 with worked examples

What is a VoIP billing increment?

A VoIP billing increment is the pair of numbers a carrier uses to round a call’s duration up before the per-minute rate applies: a minimum, billed on every answered call, and a step, billed for each block after it. Koda Voice states both on its rate deck; the increment, not the rate, sets what a call costs.

Carrier pricing pages write the two numbers as initial/subsequent seconds, so 6/6 reads “six-second minimum, six-second step.” The step decides how much rounding happens at the end of a long call. The minimum decides what a short call costs, and short calls are where conversational calling lives: calls that reach a voicemail greeting, wrong numbers, quick “call me back later” answers and appointment confirmations all end within seconds. Every one of them is billed at least the minimum.

What do 6/6, 60/60, 30/6 and 1/1 mean?

The four common notations all follow the same initial/subsequent-seconds convention: the first number is the minimum billed on every answered call, the second is the step applied after it.

Two cautions apply. First, 1/1 in this convention means one second, not one minute; a rate deck that writes 1/1 without naming the unit should be read as a question, not an answer. Second, increments can differ by destination on the same deck, so read the increment column for the destinations you actually call, not the one printed at the top of the sheet.

Worked example: 11-, 62- and 96-second calls under every increment

The billing arithmetic is the same for any carrier and any increment:

1. Take the call’s answered duration in seconds.
2. If the duration is at or below the minimum, bill the minimum.
3. Otherwise subtract the minimum, divide the remainder by the step, round up to a whole number of steps, multiply back, and add the minimum.

Applied to three durations that conversational traffic produces every day (an 11-second call that reaches a voicemail greeting, a 62-second live conversation that runs two seconds past a minute, and a 96-second confirmation callback), the four increments bill as follows.

Reading the rows: the 11-second call is billed 60 seconds under 60/60, 5.45 times its length. The 62-second call bills the same 66 seconds under 6/6 and 30/6, because 30 is itself a multiple of six; those two increments produce identical bills for any call of 25 seconds or longer, because 6/6 also rounds a 25- to 30-second call up to 30 seconds; they differ only on calls of 24 seconds or less. The 96-second call bills exactly 96 seconds under three of the four increments, because 96 is a multiple of six, and 120 seconds under 60/60.

How does the increment change the effective rate for short calls?

The effective rate is the headline rate multiplied by billed seconds divided by actual seconds. Rounding only ever goes up, so the multiplier is never below 1.00, and at any headline rate the multiplier is the whole story.

Real traffic is a mix of durations, so the effective rate is a weighted average. Take an illustrative batch of 100 answered calls, with proportions chosen to show the arithmetic rather than measured from any network: 60 calls of 11 seconds, 30 of 62 seconds and 10 of 96 seconds. Actual talk time is 3,480 seconds, or 58 minutes.

On this mix, 60/60 bills 2.3 times the seconds that 6/6 bills (8,400 divided by 3,660). A 60/60 rate would have to be below 44 percent of a 6/6 rate before it cost less for the same calls. Shift the mix toward longer calls and the gap narrows; shift it toward shorter calls and it widens.

When does a lower 60/60 rate beat a higher 6/6 rate?

A lower 60/60 rate beats a higher 6/6 rate only when the calls are long enough that minute rounding adds little to each one. The test is your own call-duration distribution, not the rate card, and it takes a spreadsheet:

1. Export a month of call detail records from your current phone system or provider, with the answered duration of every call.
2. Add one column per candidate increment and round each duration using the three-step arithmetic above.
3. Sum the billed seconds in each column and divide by 60 to get billed minutes per increment.
4. Multiply each total by the corresponding headline rate, then compare the totals, not the rates.

Two patterns follow from the arithmetic. Traffic with many short calls, such as customer follow-up, appointment confirmations and prospecting conversations, favors the smallest minimum; on a mix like the one above, a 60/60 rate needs to be under about 44 percent of the 6/6 rate to break even. Traffic with long calls, such as support conversations that run several minutes, narrows the gap, because the rounding is a smaller share of each call.

When does billing start, and what else on a rate deck changes the bill?

Billing on a well-written rate deck starts at answer supervision, the moment the called party picks up, and stops at hangup; ring time and unanswered attempts accrue no billable duration. That timing rule is one of five things to check on a rate deck before comparing headline rates. Ask all five, in writing, for each destination you call.

A sixth check is not on the deck at all: whether the provider holds its own carrier credentials or resells another carrier’s, which how to verify a VoIP carrier walks through registry by registry.

Why does the increment matter more than the headline rate for conversational calling?

The increment matters more than the headline rate for conversational calling because the rate is applied to billed seconds, not actual seconds, and conversational traffic has a wide spread of durations with a heavy short end. A rate deck can print a lower per-minute figure and still bill more minutes: on the batch above, the 60/60 column bills 140 minutes for 58 minutes of conversation. Teams running customer-contact operations pay the minimum on every voicemail greeting and every wrong number; the headline rate only says what a perfectly timed one-minute call would cost. Compare decks by billed minutes on your own traffic first, and by rate second.

How this applies to Koda Voice

Koda Voice LLC is a licensed U.S. voice carrier for conversational business calling, with its own Operating Company Number (OCN) 583H assigned by the National Exchange Carrier Association (NECA). Koda’s rate deck and order form state the billing increments, minimums and rates for each destination; ask for the rounding rule and any per-call charge at the same time. The website does not publish rates; the deck does, so the arithmetic on this page can be run against it before anything is signed.

• Voice termination: outbound calling to the United States and Canada, with the 62-second example repeated in the billing section of the service page.
• SIP trunking: capacity and increments are set on the order form; the page explains how trunks authenticate and what the onboarding conversation covers.
• Koda monitors answer-seizure ratio and call duration per customer and per route; your own call detail records give you the same duration distribution, and that distribution decides which increment suits your traffic.

Rates and increments are part of the first conversation, alongside the Know-Your-Customer questions described in what to expect from carrier KYC. To request a rate deck for your traffic profile, contact Koda sales.