K-factor is used to describe the virality of an app by defining the number of new users brought in by each existing user. For example, if each user who downloads an app leads to three more organic downloads within their social circle, the app’s K-factor would be 3.
K-factor is important to app developers and digital marketers because it measures both the value of a user acquisition, as well whether an app’s virality is increasing or decreasing. If an app’s K-factor is rising, so is the app’s popularity and the number of organic downloads. Similarly, if users from different acquisition channels create differing K-factors as well, that information can help guide awareness campaigns and ad strategies to target new users more likely to encourage more downloads in turn.
The most common method of calculating an app’s K-factor is multiplying the average number of download invites sent by each user by the rate at which those invitations are accepted. The formula is expressed as K= i*c where i = the average number of invites sent, and c = the conversion rate of those invitations expressed as a decimal.
For example, say a mobile retail app offers loyalty points to users who send invites to friends and family to download the app. On average, each user sends an invite to 5 other people, and invitees download the app at a rate of 20% or .2. To calculate the K-factor for the app, one would multiple the average number of invites sent by their users (5) by the acceptance rate, .2, for a K-factor of 1. (5*.2 = 1)
It’s important to remember that this method of calculating K-rate can only track the success of download invites, and does not account for organic acquisition from word-of-mouth style invitations or other forms of social influence that are difficult to track. When judging the success of user acquisition strategies, one should include more metrics than K-factor alone.
Though averages differ from industry to industry, any K-factor over 1 is considered good. Keep in mind though, that K-factor calculations can only provide a partial picture of virality, and is only one measurement of success among many.
Because of the tricky nature of K-factor calculations, it’s less valuable to judge an app’s K-factor against those of your competitors than it is to use it as an internal metric. If your K-factor is higher than your attrition rate, for example, that can be a strong indication that the app is growing and finding its audience.
The best long-term strategy for increasing the virality of an app is to focus on delivering a great customer experience and ensuring that users are enjoying the value of your app. Satisfied customers are any brand’s best advocates, though bear in mind the organic downloads they bring in may not always be trackable, so even successful apps with growing user bases can have deceptively low K-factors.
In the short term, campaigns that focus on encouraging referrals from satisfied users can lead to improving an app’s K-factor. Try some of these strategies: