Per-second billing charges each call for its exact length. 60/60 billing rounds every call up to the next full minute, with a one-minute minimum, so an 8-second call costs as much as a 60-second one. At the same headline rate, the gap depends on how short your calls are: in the two worked examples below it ranges from 13% to 52%.
How billing increments are written
Carriers describe billing with two numbers: the minimum billed period, then the step used after it, both in seconds.
| Notation | Minimum | Then billed in steps of | An 8-second call is billed as | A 75-second call is billed as |
|---|---|---|---|---|
| 1/1 (per second) | 1 second | 1 second | 8 seconds | 75 seconds |
| 60/1 | 60 seconds | 1 second | 60 seconds | 75 seconds |
| 30/6 | 30 seconds | 6 seconds | 30 seconds | 78 seconds |
| 60/60 (per minute) | 60 seconds | 60 seconds | 60 seconds | 120 seconds |
The headline rate per minute means little until you know the increment. A low rate billed 60/60 can cost more than a higher rate billed per second.
Why rounding adds up
Two effects drive the difference:
- The minimum. Any call shorter than the minimum is billed as the minimum. Contact centers produce many very short calls: wrong numbers, immediate refusals and answering machines detected and dropped within seconds.
- The rounding. For calls longer than a minute, 60/60 rounds the last partial minute up. If the seconds past the last full minute are spread evenly, that adds about 30 seconds per call on average.
The second effect gives a rule of thumb for traffic without many very short calls: the extra cost of 60/60 is roughly 0.5 divided by the average call length in minutes.
| Average call length | Approximate extra cost of 60/60 |
|---|---|
| 2 minutes | 25% |
| 3 minutes | 17% |
| 5 minutes | 10% |
| 10 minutes | 5% |
For typical contact center calls of two to three minutes, that puts the difference at roughly 15 to 25%. Short calls make it much worse, as the first example shows.
Worked example 1: an outbound campaign with many short calls
Assumptions: 10,000 answered calls in a month, an illustrative rate of €0.020 per minute on every offer, and the call-length mix below. Answering-machine detection hangs up on machines after about 8 seconds.
| Call type | Calls | Length | Per-second (minutes) | 30/6 (minutes) | 60/60 (minutes) |
|---|---|---|---|---|---|
| Answering machines | 4,000 | 8 s | 533.3 | 2,000 | 4,000 |
| Quick refusals | 3,000 | 40 s | 2,000 | 2,100 | 3,000 |
| Short conversations | 2,000 | 2 min 10 s | 4,333.3 | 4,400 | 6,000 |
| Full conversations | 1,000 | 6 min 20 s | 6,333.3 | 6,400 | 7,000 |
| Total | 10,000 | 13,200 | 14,900 | 20,000 | |
| Cost at €0.020 per minute | €264.00 | €298.00 | €400.00 |
Same headline rate, very different invoices. 60/60 costs €136 more than per-second billing, or 51.5% more. Put another way, the 60/60 offer advertised at €0.020 per minute really costs €400 ÷ 13,200 = €0.0303 for each minute that actually took place.
The rule of thumb alone would predict about 38% for an average call of 1.32 minutes. The rest comes from the 7,000 calls shorter than a minute, each billed as a full one.
30/6 lands in between at 12.9% more, and most of that comes from the 30-second minimum on machine calls. A 60/1 offer, with a one-minute minimum and per-second billing after it, would come to €353.33 here: 34% more than per-second, entirely because of the minimum.
Worked example 2: a retention campaign with longer calls
Assumptions: 5,000 answered calls worked in preview mode, so no machine detection, with longer conversations. Same rate of €0.020 per minute.
| Call type | Calls | Length | Per-second (minutes) | 60/60 (minutes) |
|---|---|---|---|---|
| Short calls | 1,000 | 45 s | 750 | 1,000 |
| Standard calls | 2,500 | 3 min 20 s | 8,333.3 | 10,000 |
| Long calls | 1,500 | 7 min 30 s | 11,250 | 12,000 |
| Total | 5,000 | 20,333.3 | 23,000 | |
| Cost at €0.020 per minute | €406.67 | €460.00 |
Here 60/60 costs €53.33 more, or 13.1%. The average call lasts just over four minutes, so the rule of thumb predicts about 12%; the short calls push it slightly higher. Longer calls dilute the rounding, which is why the billing increment matters most for outbound campaigns and least for long service conversations.
Other line items that change the real price
Increments are only part of the picture. Check these on every quote:
- Connection fees. Some offers add a fixed charge per answered call. A hypothetical fee of €0.01 per call adds €100 to example 1, which is 38% on top of the per-second invoice.
- Minimum call charges. A minimum charge per call works like a billing minimum, even when the increments are per second.
- Which calls are billable. Billing normally starts when a call is answered, and calls answered by voicemail count. Check whether failed or unanswered attempts carry any charge.
- Destination rates. Mobile and landline rates often differ, and so do countries. Your blended rate depends on the mix in your lists.
- Commitments. Monthly minimums, bundles that expire and minimum terms change the effective price when your volume varies.
How to compare two offers
- Export a full month of call records, with durations in seconds and the destination type of each call.
- Re-rate every call under each offer: minimum, increment, destination rate and any per-call fee.
- Add monthly fees and commitments.
- Divide each total by the minutes that actually took place. That effective rate per real minute is the number to compare, not the headline rate.
- Repeat with a month of different traffic, such as a campaign launch, to see how sensitive each offer is to your call mix.
If you don't have call records yet, build a call-length mix like the tables above from your best estimates and test it under each offer.
Questions worth asking every provider before you sign:
- What is the billing increment for each destination, and is it the same for landlines and mobiles?
- Is there a minimum charge or a fee per call, and does it apply to calls answered by voicemail?
- Are failed, busy or unanswered attempts ever charged?
- Can you export call records with durations to the second, so you can check the invoice?
- What happens to unused minutes in a bundle at the end of the month?
Where per-second billing matters most
- Predictive campaigns with answering-machine detection, which create many calls lasting a few seconds. More in answering-machine detection: how it works.
- Old or unqualified lists with many wrong numbers and immediate hang-ups.
- Calls that are short by design: appointment confirmations, quick surveys, qualification calls.
- Any team that pays for every minute rather than a flat calling plan.
It matters least for long service conversations and for teams on a flat unlimited plan, where the question becomes whether the plan pays for itself. See unlimited calling or pay as you go.
How OVOKY bills voice
OVOKY bills voice per second, with no minimum and no connection fee. Pay-as-you-go rates at the time of writing:
| Destination | Rate per minute, billed per second |
|---|---|
| France, landlines | €0.007 |
| France, mobiles | €0.024 |
| Belgium, landlines and mobiles | €0.028 |
Calls draw on a prepaid balance in euros that you top up by card, PayPal, Mollie, crypto or bank transfer. Teams with heavy predictive volume can choose an unlimited calling plan per agent instead. Current prices are on the pricing page, and the Cost & Consumption Trend report in OVOKY reports shows daily cost and minutes, so you can check your effective rate yourself.