The whale curve: which customers really make you money

Tradies Sidekick team · 9 November 2026

In most trade and service businesses a handful of customers earn most of the profit, while a few quietly cost money once labour and materials are counted. Revenue won't tell you which is which; a whale curve will.

Customer profitability analysis, in plain terms

Customer profitability analysis works out the profit each customer leaves you after the cost of serving them. For a trade business that cost is mostly the labour hours and materials on their jobs, plus a share of travel and admin.

The results surprise most owners. Your busiest customer can be one of your least profitable, because their jobs always run over or they live 40 minutes from everyone else.

What a whale curve shows

Line up every customer from most profitable to least, then plot the running total of profit as you add each one. The line climbs steeply through your best customers and peaks, then drops as the loss-makers at the end pull it back down; drawn out, it looks like a whale's back.

This business would make $18,000 more with 25 fewer customers, and have more free time too. The top 20 alone earn 94% of the final profit.

What to do with unprofitable customers

Dropping customers comes last. Work through these in order:

1. Reprice. Most loss-makers are on an old rate or a guess. Rework their regular job in the quote calculator above at your real costs and put the new price to them; many will accept.
2. Rescope. If the job keeps running over, change what's included or charge for the extras separately.
3. Reschedule. Travel alone can make a customer unprofitable, and booking them on the same day as their neighbours often fixes it.
4. Let them go, politely. If nothing else works, those hours are worth more spent on a customer who pays. Recommending another business is fine.

How to work out profit per customer

For each customer you need what you invoiced them (ex GST, less credit notes), the labour hours on their jobs at your real hourly cost, and the materials used. In practice that means matching each ServiceM8 client to its Xero contact and adding up their jobs, which is slow going in a spreadsheet.

Tradies Sidekick does it automatically. It ranks every customer by real profit, draws your whale curve and plots each customer's revenue against margin, so the ones worth looking after stand apart from the ones costing you. Loss-makers show in red, with a list you can work through.