LettrLabs tracks a wide range of metrics to help you understand how your direct mail is performing. This guide defines every metric in the catalog, in plain language, grouped by category. Think of it as a glossary you can come back to whenever you see a term you don't recognize.
Results Summary
These metrics summarize the overall revenue impact of a mailing.
Revenue: The total dollar amount of sales attributed to the mailing.
ROAS (Return on Ad Spend): Revenue divided by what you spent, showing how many dollars came back for every dollar spent. For example, a placeholder ROAS of 4.0 would mean $4 in revenue for every $1 spent.
AOV (Average Order Value): The average dollar amount of each attributed order.
Revenue Per Recipient: Total attributed revenue divided by the number of people mailed.
Estimated Revenue: A projected revenue figure, used when full attribution data is still settling.
Estimated ROAS: ROAS calculated using Estimated Revenue instead of final attributed Revenue.
Estimated AOV: Average order value calculated using estimated figures.
Conversions
These metrics track purchases and the cost efficiency of generating them.
Conversions (Purchases): The total number of purchases attributed to the mailing.
Purchase Rate: The percentage of mailed recipients who made a purchase.
CPP (Cost Per Purchase): Your mailing cost divided by the number of purchases.
Converted Recipients: The number of unique recipients who made at least one purchase.
Conversion Rate: The percentage of unique recipients who converted at least once.
CPA (Cost Per Acquisition): Your mailing cost divided by the number of converted recipients — a close cousin of CPP, but measured per customer acquired rather than per purchase.
Incrementality
This category measures the true lift your mailing generated, beyond what would have happened anyway.
iROAS (incremental ROAS): The return on ad spend calculated using only the incremental revenue your mailing caused, determined by comparing a mailed group against a Holdout group that received no mailing. This isolates the effect of the mailing itself, rather than crediting sales that would have happened regardless.
Leads
These metrics apply when your mailing is designed to generate leads rather than (or in addition to) direct purchases.
Leads: The total number of leads attributed to the mailing.
CPL (Cost Per Lead): Your mailing cost divided by the number of leads generated.
Revenue per Lead: Total attributed revenue divided by the number of leads.
Closing
This category measures how effectively leads turn into paying customers.
Close Rate: The percentage of leads that eventually convert into a purchase or sale.
Mailing Details
These are the underlying counts and costs behind every other metric.
Recipients: The number of people who were mailed.
Holdout Recipients: The number of people set aside in a Holdout group — people who match your audience but were deliberately not mailed, so their results can be compared against your mailed group.
Cost: The total dollar cost of producing and sending the mailing.
Holdout-only metrics
Some metrics exist only as part of a Holdout-group comparison — there is no equivalent version of these for a mailing that doesn't include a Holdout group.
First Order Revenue (Holdout): Revenue from a customer's very first order, compared between the mailed group and the Holdout group.
Repeat Conversions (Holdout): The count of repeat purchases (a customer's second, third, etc. order), compared between groups.
Repeat Conversion Rate (Holdout): The percentage of recipients who made a repeat purchase, compared between groups.
Estimated Revenue Per Lead (Holdout): Projected revenue per lead, compared between the mailed and Holdout groups.
Response Rate (Holdout): The percentage of recipients who responded in some measurable way, compared between the mailed and Holdout groups.
Where you'll actually see these
With this many metrics, it helps to know where they show up day to day. The order-level Analytics card — covered in detail in "Understanding Your Order's Analytics" — shows only 5 of these metrics by default: Revenue, Conversions, Leads, ROAS, and Conversion Rate. If you're looking at a holdout test specifically, the holdout-testing view surfaces iROAS as its headline metric.
The rest of the metrics defined above are part of LettrLabs' broader attribution and analytics system — they exist and are calculated, but this article is defining what each one means, not asserting that every single one is individually surfaced on the order card itself.
Unverified: exactly where in the product each of these metrics beyond the order card's default 5 and the holdout iROAS is displayed (e.g. in reports, exports, or other views) was not fully walked through live for this guide — this article defines what each metric MEANS, not a guarantee of where you'll see every one of them in the UI today.