Every growth agency will show you a CAC vs LTV slide. Almost none of them run it correctly for fashion.
The standard formula, lifetime revenue divided by acquisition cost, was built for categories where a sale is a sale. Fashion doesn't work that way. A meaningful share of what gets counted as "revenue" in that formula walks back through the returns process weeks later, and a meaningful share of what's left was already discounted to make the sale happen.
Run the standard formula on a fashion brand and you'll usually get a healthier-looking ratio than the business can actually support.
Where the standard formula breaks for fashion
Return rates are structural, not incidental.
Apparel and footwear routinely see return rates between 15 and 30 percent, driven by sizing uncertainty alone. A standard LTV calculation using gross revenue treats every one of those orders as fully realized value. It isn't. Refunded orders come back off revenue, and the acquisition cost that brought that customer in doesn't come back at all.
Discounting compounds the gap.
Fashion runs on promotional cycles more than most categories. If 40 percent of orders come through a 20 percent off code, your realized LTV per customer is meaningfully lower than a top-line revenue number suggests, and it's lower again once you net out the returns sitting inside that discounted revenue.
CAC is usually understated too.
Most CAC calculations only count paid media spend. They leave out influencer fees, affiliate commissions, and the portion of creative production cost tied directly to acquisition campaigns. For fashion brands running heavy influencer and UGC-driven acquisition, this can understate true CAC by a wide margin.
The corrected formula
Instead of:
LTV = Average Order Value x Purchase Frequency x Customer Lifespan
Use:
Net LTV = (Average Order Value x (1 minus Return Rate) x (1 minus Average Discount Depth)) x Purchase Frequency x Customer Lifespan
And instead of:
CAC = Ad Spend / New Customers
Use:
Fully Loaded CAC = (Ad Spend + Influencer and Affiliate Costs + Acquisition-Specific Creative Cost) / New Customers
The ratio between these two numbers, not the standard version, is what actually tells you whether a channel or campaign is building a sustainable business.
What this looks like in practice
Take a brand with a reported LTV:CAC of 3.5:1 using standard math. Average order value of $110, purchase frequency of 1.8 times a year, average customer lifespan of 2 years, and a blended CAC of $35 across channels.
Standard LTV: $110 x 1.8 x 2 = $396. Against a CAC of $35, that's a 11.3:1 ratio, which would read as exceptional.
Now factor in a 22 percent return rate and an average discount depth of 18 percent across orders, plus influencer costs that add another $6 to true CAC per customer.
Net LTV: $110 x 0.78 x 0.82 x 1.8 x 2 = $253. Fully loaded CAC: $41.
The corrected ratio comes out to roughly 6:1. Still healthy, but nearly half of what the standard formula showed, and a very different number to base a scaling decision on.
Why this matters for how you scale
An 11.5:1 ratio tells you to pour budget into every channel that's working. A 6:1 ratio tells you to be more selective about which channels and which SKUs get incremental spend, because the margin for error is smaller than it looked. Brands that scale off the inflated number are usually the ones that hit a cash flow wall six months later without understanding why, because the unit economics were never as strong as the dashboard suggested.
Before your next scaling decision
If your CAC vs LTV math doesn't currently factor in return rate and discount depth by SKU, the ratio you're using to make budget decisions is optimistic by definition, not by a small margin.
A proper unit economics review pulls actual return data and discount depth from Shopify, layers it against fully loaded acquisition cost, and rebuilds the CAC vs LTV picture per channel and per product line. That's the version of the number worth scaling against.