(Outline of Dunbar’s thesis on friendship capacity in previous posts: https://jotsandscribbles.blog/2023/09/24/the-definition-and-value-of-friendship/ and https://jotsandscribbles.blog/2023/09/18/introduction-to-friends-by-robin-dunbar/)
Robin Dunbar suggests (based on psychology and sociology) that human beings have an average capacity for 150 friends. These friends are in rings of closeness, each ring including the previous ring and being roughly 3 times the previous one. So a closest group of 5, then a group of 15, then a group of 50, then a group of 150.
Ian Paul wrote about this on his blog, applying it to church size: What is the ideal size for a church? | Psephizo In it, he suggest that churches should operate at all the levels Dunbar suggests: a small group if 4-5 for change, a homegroup of 12-15, pastorates (3 homegroups) of 40-50, and churches looking to plant at 150. It’s a helpful attempt to look seriously at how people’s relational capacity affects church size. But there is a rather obvious problem with the application. If the ideal church is 150 because the maximum number of friends we can have is 150, then what friends do we have outside the church? We can only use Dunbar’s number of 150 as the size of the church if the church is a commune!
But we want people to have lots of friendships beyond the church. Family is usually 30-50% of our friendship group, and if you have moved for study and work, most of your family aren’t in your church. It is a safeguard against cult-like tendencies to have friends in other churches. And if we are to be salt and light to the world, then we need to have friendships with non-churchgoers whether neighbours, old friends, fellow hobbyists or work colleagues.
So what should we expect when it comes to friendship at church? Well if an average person has capacity for 150 friendships (with a range of 100-200), 50 of those slots are taken by family. Another 50 are taken with old friends, neighbours, work colleagues and friends from other clubs and hobbies. So only 50 friendship slots are available for church. If we think everyone in church should be friends with everyone else in church, then we should be looking to plant new churches once we hit 50-60 people.
Ands that might be right. But at that size churches may struggle with staffing, true diversity, and the gifts needed to manage an organisation. So perhaps its ok not to be friends with everyone at church. Perhaps, the issue is whether the church is a size where everyone can know each other’s name and a bit about them. We’re not all friends, but we are a community that recognises and can communicate with everyone. The church size for this will be set by the 500 person capacity for [name plus some details] minus [the number of such relationships people typically have (and even need) beyond the church]. Many work colleagues will be in this [name plus some details] category for example.
The book does not provide figures for this but my guess is that somewhere between a church size of 100 and 250 people stop knowing most of the other regular attenders even at the level of name, basic family connections, and a few key facts. So somewhere in that size transition there is a dramatic change from a community who know each other to an organisation that people relate to.
In most medium size churches (more that 60, less than 200) if people have 50 friendships in church (including relationships with children if you relate regularly and well) then they may not be “friends” with the majority of the church. And that is ok. In practice, many people will be friends with their homegroup (15 people), people in their ministry team and served by the ministry team (15 people) and peer or interest groups in the church (the young adults, the mums with under 2s, the over 60s, the board gamers, the footballers etc).
I think it is important to set right expectations here, otherwise people and churches can be doing well but feel like they are failing. The emphasis on church as community and family is right and good. But a church of 150 is an extended family, and you don’t see all your second cousins very much. It is ok to feel like only a half or a quarter of the church are your friends. Time limits and other relationships beyond church mean that will be typical.
Church leaders will typically devote more of their time and relational energy to church. But even there, a single church leader can’t be friends with everyone in the church as the church grows. He may have a higher than normal relational capacity (or he may not!) and he may prioritise church relationships, but he still can’t have more than 150 friends in church. Many pastors can only manage 60-80 church friends, if they are introverts and have family, old friends, and non-church local friends. So if everyone is to be friends with a church leader (and that seems good), there will need to be plurality of church leaders.
Jots and Scribbles 
As a data point – I grew up in a church of 40 people (including kids). Everyone knew everybody to a fairly deep level. Everyone was active in service, with the result that quite a few things were done by people who weren’t very good at them. Initally I was going to describe this as a minus, but I suspect God is less interested in the technical proficiency of the preaching, or the music or the admin than we are, so I think the main drawback is that 40 people isn’t really a viable diverse group – for example at that size either every adult is a parent of school age kids, or your kids ministry has age group holes in. Either option is tricky to sustain.
The church I’m in now has a congregation of 200. I’ve been a very regular attender for 17 years and I couldn’t put names to half the faces. My wife would do much better since we had kids and she went part time and got more involved in mid week families stuff.
A while ago our minister mentioned a study which found church congregation sizes had frequency peaks at certain points on the graph. I can’t remember the details, but the theory was that a successful church grows until it hits the limits of its current structure. Some churches change structure and carry on growing, others stick at that point (or plant, perhaps a better way to solve it). I have an idea the key numbers were something like 100 and 250, but this was years ago and I may not be remembering correctly. I can certainly imagine there are key thresholds of approximately ‘all the members know each other’ and ‘the minister knows all the members’.
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I agree that true diversity is one of the key limitations of smaller churches. Especially because most people want to have a few people like them. So if you want peers (2-3 other people at your stage of life) in a church of 40, there will be gaps. And because of aging, a small church that feels fun with lots of families will feel a bit empty and frail 20 years later if there is not growth.
My experience is that 80-100 probably is the point you go from medium-small to medium-large. The key thing is that there are too many people and too many tasks for one person to handle, which means creating the teams and structures for sharing tasks- and I can imagine those structures working ok till 200 people.
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