Free voice call apps, which use data to place calls, can offer a cheaper way to keep in contact with friends abroad and come to the rescue when you’ve used up your monthly minute quota. However, with multi-gigabyte data plans still often coming at a premium price, the busiest chatters out there could soon eat into their monthly allowance using voice over data calls.

To shed some light on the issue, we’ve gone back over our list of 10 free call apps to investigate just how much data these apps end up consuming. In the list you’ll find popular apps such as Hangouts, Skype, WhatApp and Viber, as well as regional favourites including Line and Nimbuzz.

The test method

For our test, we subjected each of these 10 apps to three separate one minute calls and recorded the amount of data used by the app after each call. These three totals were then averaged together to produce the result.

Both sides spoke for 30 seconds each during the one minute call, to simulate a two way conversation. All of the test runs were conducted over a 4G network on both ends, with both phones running the latest versions of each app from the Play Store and the same Android operating system version, just to be extra safe.

The results

We can instantly spot a huge difference between the leanest and the heaviest data consuming applications. Interestingly, many of the most well-known apps, such as Hangouts, Skype and WhatsApp, consume by far the most data, while KakaoTalk, Nimbuzz and Line all consume comparatively smaller amounts of data. Facebook Messenger also makes a bit of a surprise appearance as one of the most data efficient ways of placing a voice call.

Perhaps a little worryingly for Skype users, the app consumes over 2.7 times the amount of data per minute than the most economical apps. WhatsApp consumers 2.3 times the data of KakaoTalk, while Hangounts and Tango consume around twice the data each minute. Over the course of an hour’s worth of calls, the difference between Skype and KakaoTalk works out to around 33.4MB, which might be a point worth considering if you’re on a more limited data plan and like to talk.

Skype consumes over 2.7 times the amount of data per minute than the most economical apps

Magic Jack and Viber both consume a little more data than others, but are still much economical choices than the more established apps. These may be the best choice if you’re looking for a balance between call quality and data usage.

To be fair to the big brands, we do know that Skype implements a rather intelligent codec that is capable of various sample and bit rates. We went back to see if switching down to a 3G network, with more limited bandwidth, would make any difference to the data consumed, but the results came back well within the margin for error. We can conclude that a 3G connection is more than good enough for the best voice call quality that Skype and the other apps have to offer on Android, so you’ll probably always find that these apps consume around this amount of data, regardless of a 3G, 4G or WiFi connection type.

While the big companies may be able to spend some cash on extra bandwidth and servers, Kakao, Nimbuzz and Line most likely make use of a lower quality communication to save on expensive server bandwidth, which has the added benefit of saving us data usage too.

Of course, data usage is just a small aspect of a voice call app. If you would like a closer look at the features available with these apps, be sure to check out our list of to 10 free voice call apps.

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