The revenue your flows aren’t collecting.

How this calculator works

Four numbers go in, and only two of them do arithmetic. The other two are there to stop you misreading the answer.

Total attributed email revenue and flow revenue give you your current flow share. Subtract one from the other and you have campaign revenue, which is the anchor for everything that follows. The benchmark is expressed as a share — 41% of email revenue coming from flows — so you cannot simply multiply your current total by 41% and call the difference a gap. Doing that quietly assumes campaign revenue shrinks as flow revenue grows, and that is not what happens. Flows are triggered by behaviour that is already occurring on your site. They add revenue rather than moving it around.

So the model holds campaign revenue fixed and asks a different question: if campaigns are the 59% that isn’t flows, how large would flows have to be for the split to come out at 41 to 59? That is campaign revenue multiplied by 41 divided by 59, and the gap is that target minus what your flows do today. Total email revenue rises by exactly the same amount, which is why the lift figure in the result block is smaller than the gap looks.

Sessions and list size never enter the gap calculation. They are on the page because a flow revenue number without a denominator can’t be interpreted. Two brands both earning $19,000 a month from flows are in completely different situations if one has 12,000 profiles and the other has 200,000, and the per-profile line is what tells you which conversation you are in.

What the 41% actually is

Automated flows drive around 41% of email revenue from roughly 5% of sends, across Klaviyo’s benchmark set of more than 183,000 brands. Two numbers, and the second is the one that matters. Five percent of sends producing forty-one percent of revenue is a statement about revenue per recipient — flows run around 18 times a campaign — and it is why a flow stack built once at launch and never revisited is the most common seven-figure oversight in this category.

It is also why the gap is so rarely a copywriting problem. Campaigns are visible: somebody has to send one every week, so they get attention, budget and opinions. Flows are invisible. They run whether or not they work, and nobody opens the account to check. The typical $5M brand has a welcome series written before product-market fit, a one-touch abandoned checkout, a post-purchase flow that says thank you and nothing else, and no replenishment logic at all — usually because the person who built them left two years ago.

The gap is a build order, not a number

Once you have a dollar figure, the useful question is which flows close it. For a brand whose customers finish the product and rebuy it, the order is fairly consistent, and it is not the order most agencies work in.

1. Replenishment and reorder. Timed against actual consumption data rather than a flat 30-day guess. This is the flow a retention specialist builds and a generalist does not, and on a product people finish and rebuy it is usually the largest single line in the gap.
2. Post-purchase education. Timed to the product’s real usage curve. For supplements this is the highest-return flow you can build, because the month-three cliff is an education problem rather than a product one.
3. Abandoned checkout, taken to three touches. Three-email sequences generate roughly 6.5 times the revenue of single emails on the same traffic, and most brands are still running one.
4. Welcome, properly segmented. Split by first product and by subscription versus one-time. Someone buying a starter kit for the first time needs a different sequence from someone reordering a refill they already know.
5. Winback and sunset, last. Segmented by why they left, with real list hygiene attached so deliverability doesn’t degrade while you chase the gap.

Underneath all five sits deliverability — authentication, sending reputation, engagement-based segmentation, suppression logic. Everything above is worth nothing if the sends land in Promotions. The full build is described on the lifecycle flows page.

Where this model stops being true

Attribution is generous by design. Every number here comes out of your ESP’s attribution window, which will happily credit a flow for a purchase somebody was going to make anyway. That inflates both sides of the ratio, so the share is more trustworthy than the absolute dollars. Treat the gap as a well-scaled estimate rather than a receivable.

The benchmark is a median across every category. A brand with a genuine replenishment rhythm — supplements, coffee, skincare, home care — should clear 41% comfortably; a considered-purchase brand with an eighteen-month repurchase cycle reasonably won’t. If your category is closer to the second, read the gap as directional and benchmark against your own best month instead.

One month is one month. A promotion, a launch or a stockout will distort the campaign side badly, and because campaign revenue is the anchor, it distorts the target with it. Run three months and take the middle one.

A share is not a ceiling. Hitting 41% is not the goal; the absolute number is. A brand that doubles flow revenue while also growing campaigns will show a flow share that has barely moved. Watch the dollars, and use the share only to tell you whether the flow stack is carrying its weight.

What to do with the result

1. Export flow-level revenue and revenue per recipient for the same month and rank your flows against the table above. The gap almost always concentrates in two or three of them.
2. Check which flows don’t exist at all. A missing replenishment flow shows up as a zero, not as underperformance, and zeroes are easy to scroll past.
3. Put the annual gap next to the cost of the build — a fixed-cost project against a recurring return.
4. Re-run this in 30 days. Flow revenue moves inside a month of launch, though replenishment timing needs a full purchase cycle before it reads properly.