"Our customers stay forever. Lifetime value is basically infinite."
The founder pitching that line had a 4% monthly churn rate. His actual lifetime was 25 months. His actual LTV was £1,200 against a CAC of £900.
He had a hobby that looked like a business in the dark.
This is what LTV does. It turns optimism into arithmetic. And the arithmetic decides whether your venture is fundable, sustainable, or terminal.
The number that quietly kills startups
Customer lifetime value is the profit you make from one customer over the time they stick around, discounted for the cost of the money you raised to acquire them.
Read that again. Three things to notice.
Profit, not revenue
The most common LTV mistake is adding up revenue streams and calling it done. Revenue is what they pay you. LTV is what's left after you've paid for the thing. If your gross margin is 30%, you're keeping 30p in the pound, and your LTV is a third of what you thought.
The time they stick around, not forever
If your monthly retention is 96%, your customer is around for about 25 months on average. That's it. Plug in your real churn rate, not your wishful one.
Discounted by your cost of capital
A pound of profit next year is worth less than a pound of profit today, because you had to raise money at a cost to get there. For a seed-stage venture, your cost of capital is somewhere between 35% and 75%. Future profits get hammered.
Get any of these wrong and your LTV is fiction.
What actually goes in
Aulet's framework is brutally specific. Six inputs.
- One-time revenue. The upfront price they pay you. £10,000 for the widget.
- Recurring revenue. Subscription fees, maintenance contracts, repeated purchases. The 15% annual maintenance fee on the £10,000 widget = £1,500 a year after year zero.
- Upsell revenue. The additional products they buy with minimal sales effort. Be honest. Most "upsell potential" is a slide in a deck, not a real revenue stream.
- Gross margin per revenue stream. What's left after COGS. The widget might be 65% margin. Maintenance is usually 85%+. Software is mostly 80%+.
- Retention rate. Per year, the percentage of customers still paying you. The other side of the coin is churn — your retention's evil twin.
- Cost of capital. Treat this as a tax on the future. Higher for seed, lower for Series B.
Five years of profit, summed, discounted. That's LTV.
The arithmetic that kills the slide deck
Run the widget example.
Year zero: £10,000 sale at 65% margin = £6,500 of gross profit. Half-year of maintenance at 85% margin = £638. Total year zero = £7,138.
Year one onwards: £1,500 maintenance at 85%, retained at 90% per year, discounted by the 50% cost of capital. Year one is about £1,275 of profit, present-valued. Year two is half of that. Year five is barely there.
Sum it. You end up somewhere around £9,500 of LTV on a £10,000 sticker price. Most of that is the original sale. The "lifetime revenue" you put in the pitch deck is mostly an illusion because future cash gets gutted by the discount.
That's the disciplined version. The undisciplined version says "£10K sticker, plus £1,500 maintenance for 5 years, so £17,500 LTV". They're off by a factor of nearly two and they'll find out when their cash runs out.
The 3:1 rule
LTV is meaningless on its own. The number that matters is LTV divided by CAC.
The standard SaaS benchmark is 3:1. Customer is worth three times what they cost to acquire. Below that, you're sprinting on a treadmill. Way below, you're funding your customers' lifestyle. Above 5:1, you're probably under-investing in growth.
An LTV of £10,000 looks great until CAC is £4,000. Then your ratio is 2.5:1, you're under-water on the benchmark, and the next round of funding gets harder.
An LTV of £2,000 looks bad until CAC is £200. Then your ratio is 10:1 and you have something venture capital wants to feed.
Always carry the ratio in your head. Never the LTV alone.
The five levers
If your LTV is too low, you have five places to push.
The business model
Subscription beats one-time for LTV but burns more capital. One-time beats subscription for cash flow but caps your upside. The model is the biggest LTV variable you control. Pick deliberately.
The gross margin
Bundle high-margin add-ons around a lower-margin core product. The classic move: printers at cost, ink at 80%. SaaS at 80% base, professional services at 50% on top.
The retention rate
A 5-point improvement in annual retention can double your five-year LTV. This is where customer success teams pay for themselves. This is why "land and expand" enterprise sales motions work.
The upsell
But only if it's real. Build upsell into the persona's needs, not into your spreadsheet. Customers who get upsold things they didn't want churn faster than ones who didn't get upsold at all.
The cost of capital
Mostly out of your control until you have traction. But early profitability lowers it. So does revenue concentration in marquee logos that lower your perceived risk to the next investor.
The bit nobody likes
You will run this calculation honestly, and your first pass will tell you the numbers don't work.
This is good news. Most founders never find out until the cash runs out. You found out at step seventeen, with a spreadsheet and a clear head.
Now you can change the variables. Move from one-time to subscription. Add a high-margin service layer. Build retention into the product. Re-price.
What you cannot do is shrug, write a higher LTV in the deck, and hope investors don't check.
They check. They've been checking since the day they wrote their first cheque. They know what 4% monthly churn does to a 25-month-old subscription business. They will know what it does to yours.
Be the founder who already knew.