Nov 12, 2018 · 4 min read

The cheapest advertising is always word of mouth. You want your customers to love your product so much they talk about it endlessly. Help them help you by engineering your product to go viral.

The Basics

In marketing, there is a concept of the ‘viral coefficient’, referred to as K.

K = Average # of times each customer tells others about your product * the percentage of those people who try your product.


  • Your product has 100 users. 50 of them invite 10 friends for 500 invitations (50 x 10).
  • Because half your users don’t invite others, the average number of invitations per user is 5. So, the first part of the K equation is 5.
  • Of those 500 who were told to try your product, 50 (10%) accept.

K, the viral coefficient is 5*.1 = 0.5

Is this good or bad?

In order for a product to go viral, you need a K above 1. The higher the better. So even though your 100 users invited 500 new ones, your product will not go viral. This may be counter-intuitive, because it seems like your product is doing great! Your 100 users managed to bring in 50 new ones, for a 50% boost. To many first time entrepreneurs this seems like a massive success, but it is not. A good K value is something like 10–20. That means that for every user you have, they bring in at least 10 new ones successfully.

What causes Virality?

The first thing to understand is that viral growth must be earned by delighting users. You cannot spend your way to virality. Many have tried, but this is just a quick way to go bankrupt.

The 5 aspects of a viral product

  • Easy to learn. A product that takes a long time to learn means that it may take a long time for it to get recommended. Usability is critical.
  • Evoke Emotion. Your product should delight your users.
  • Easy to share. Once you’ve delighted your users you want to make it effortless for them to encourage others to use your product.
  • Easy to access. You want as few barriers as possible to signing up, logging in, or anything else you need your users to do. Minimalism is a virtue.
  • Distinctive. Your product needs to stand out somehow, in a way that appeals to the tastes and identities of your users. Being good isn’t enough. A power tool might do a great job, but (almost) nobody identifies or shares how much they love their favorite drill. Find a way to connect with your user’s identity. Help them feel smart and important for sharing your product.

Ego drives virality

The last of those points should be repeated. People do not share because your product is good. They share because they want to seem cool, important, and knowledgeable to their friends. This one trait overwhelms most of the others. Snapchat was actually quite hard to use, but early adopters got to feel cool for using it and snapchat exploded. But ever since the cool factor wore off, Snapchat’s been headed downhill.

Viral Cycle Time

Once you have a viral product, you need to speed up the viral cycle. The viral cycle is the sequence where a user shares and brings in more users. They, in turn, share and bring in yet more users.

The faster you can make each of these sharing sequences happen, the faster your product will grow. Even if your viral coefficient isn’t that high, a fast cycle time can more than make up for it.

How do you improve viral cycle time?

Viral cycle time is heavily dependent on the number of actions it takes for a user to sign up, try your product, have success, and share again. For instance, a piece of content (like this article!) can go viral easy because all you have to do is copy the URL into your Facebook or linkedin feed (do that now).

A product is usually harder. A user typically needs to sign up, take a few actions in order to see if your product works for them, and then be encouraged to share.

You can remove some of this friction by allowing signup using google or facebook accounts and providing social buttons to speed up the actual act of sharing.

But the real work is making your product as slick as possible. A laser sharp focus on customer success and solving their one problem flawlessly and fast. It’s worth putting your product in front of users and watching how they use it and seeing what can be done to remove steps.


The keys to a viral product are straightforward, but that doesn’t make it easy. Be thoughtful and creative and be willing to experiment. Don’t overthink it! Your users will give you the best feedback. Be aggressive in seeking genuine and natural reactions and work towards delighting your users. Once you know you can make them happy, make them feel smart by sharing your awesome tool.

This story is published in The Startup, Medium’s largest entrepreneurship publication followed by +387,966 people.

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