Sends vs Opens, Klaviyo

Sends vs Opens for the selected period. Grouped bars comparing send volume against open volume per bucket, where the gap is the unopened share. How to read it, why it matters, and how to act on it.

Metrics type: Supporting Metrics • Category: Email Marketing

Send volume next to open volume, side by side per period. The visible gap between the bars is the unopened share, the part of every send that never got looked at.

At a glance

Grouped bars comparing how much you sent against how much got opened, per period bucket. The send bar is your reach; the open bar is the slice that registered an open; the gap between them is the unopened share. This visual makes the absolute scale of your missed audience obvious in a way a percentage cannot: a 45% open rate sounds healthy until you see the open bar is less than half the height of the send bar. Because the open bar is inflated by Apple Mail Privacy auto-opens, the real human gap is even wider than the chart shows, so treat the bars as directional, not literal.

What it counts	Two series per bucket: send or delivered volume (recipients / delivered) and open volume (opens_unique), drawn as grouped bars over the selected window.
API endpoint + statistics field	POST /api/campaign-values-reports and GET /api/metric-aggregates, returning recipients or delivered for the send bar and opens_unique for the open bar.
Email vs SMS aggregation	Email only. SMS has no open concept and is excluded from both bars.
MPP impact	On the open bar. Apple MPP auto-opens inflate opens_unique, so the open bar overstates real human opens and the visible gap understates the true unopened share.
Chart type	Grouped bar.
Time window	30D vsP
Alert trigger	A widening gap between the send and open bars over consecutive buckets, which signals falling open engagement or deliverability erosion.
Roles	owner, marketing

Calculation

Calculated automatically from your Klaviyo data. See the At a glance summary above for what the metric tracks and the worked example below for a typical reading.

Worked example

An illustrative coffee subscription brand on Klaviyo with a weekly campaign cadence. Reading the dashboard on 14 Apr 26 for the trailing 30 days (14 Mar 26 to 12 Apr 26), the grouped bars by week look like this (illustrative figures):

Week	Sends	Unique opens	Unopened (gap)	Open rate
14-20 Mar 26	50,000	22,500	27,500	45.0%
21-27 Mar 26	51,000	22,950	28,050	45.0%
28 Mar-3 Apr 26	50,500	20,200	30,300	40.0%
4-12 Apr 26	52,000	18,720	33,280	36.0%

Week 1 gap = 50,000 sent - 22,500 opened = 27,500 unopened (55%)
Week 4 gap = 52,000 sent - 18,720 opened = 33,280 unopened (64%)
The unopened bar grew by ~5,780 while sends barely moved

Five observations:

1. Even in the best week, the unopened gap is larger than the open bar. At a 45% open rate, 55% of every send went unopened, 27,500 of 50,000. The grouped-bar view makes that scale visceral in a way the headline “45% open rate” does not: more than half your reach saw nothing.
2. The gap widens across the four weeks while sends stay flat. The open bar shrank from 22,500 to 18,720 on near-constant sends, so the unopened bar grew from 27,500 to 33,280. A gap widening on stable send volume is the signal: engagement or deliverability is slipping, not just normal variation.
3. The MPP caveat makes the real gap worse than drawn. A meaningful share of those open bars are Apple Mail pre-fetches, not humans. So the true human unopened share is even larger than the chart suggests. Read the bars as a directional floor on missed audience, not a literal count.
4. A widening gap usually points to inbox placement or list fatigue. When you send the same volume but fewer open, messages are increasingly landing in spam or Promotions, or the list is tiring of your cadence. Confirm with Delivery Rate and Open Rate Trend before acting.
5. The lever is not “send more”, it is “close the gap”. Pushing more volume into a widening gap just grows the unopened bar and accelerates fatigue. Better moves are tighter segmentation, subject-line testing, and pruning dormant contacts, all aimed at lifting the open bar relative to the send bar rather than raising both.

Sibling cards merchants should reference together

Sends vs Opens is a reach-vs-engagement picture. Pair it with these to act on the gap:

Card	Why pair it with Sends vs Opens
Total Sends	The send bar on its own. Use it to confirm whether a widening gap came from sending more or from fewer opening.
Opened Trend	The open bar on its own. Tracks the open-volume side of this chart over time in isolation.
Open Rate Trend	The percentage view of the same gap. The unopened share as a ratio rather than a bar height.
Engagement Funnel	Extends sends-and-opens into clicks and conversions, so you can see the whole cascade, not just the first step.
Email Open Rate	The single-period open headline. Combine with the bar view to translate a percentage into absolute missed audience.

Reconciling against Klaviyo

Where to look in Klaviyo:

• Klaviyo → Campaigns, then a specific campaign’s analytics, where recipients, delivered, and unique opens are shown side by side.
• Klaviyo → Analytics → Metrics, then the Opened Email and delivered metrics, for the two series over time.
• Klaviyo → Analytics → Performance, for the blended send-and-open picture across campaigns and flows.

Why our number may legitimately differ:

Reason	Direction of divergence
Recipients vs delivered for the send bar. If we draw the send bar from delivered and you compare against a Klaviyo view using recipients (which includes bounces), the bars differ by the bounce volume.	Send bar reads lower when based on delivered.
MPP auto-opens. Both systems count machine opens in the open bar, but a Klaviyo MPP filter, if enabled, lowers its open bar relative to ours.	Klaviyo’s filtered open bar reads lower.
Time zone. Vortex IQ buckets by UTC day; Klaviyo uses your account time zone. Sends or opens near midnight can shift buckets.	Either direction, usually marginal.
Unique vs total opens. This card uses unique opens. A total-opens Klaviyo view reads higher on the open bar.	Ours reads lower against a total-opens view.
Page caps. Campaign-values reporting pages at 50 records per pull, so very high-volume accounts may see slight aggregation truncation in both bars.	Both bars run marginally low for very large senders.

Known limitations / merchant FAQs

What exactly is the gap between the two bars? The unopened share: emails that were sent (or delivered) but never registered an open. If the send bar is 50,000 and the open bar is 22,500, the gap of 27,500 is the volume that went unopened. It is the most direct visual of how much of your reach saw nothing.

Is the open bar real, or inflated? Inflated. Apple Mail Privacy Protection auto-opens emails to pre-fetch images, registering opens with no human involved. So the open bar overstates real human opens, which means the true unopened gap is even wider than the chart shows. Read the bars directionally, not as exact human counts.

The gap is widening, what does that mean? If sends stayed flat but the open bar shrank, fewer of the same emails are being opened. That usually points to inbox-placement erosion (more landing in spam or Promotions) or list fatigue from over-sending. Check Delivery Rate and Open Rate Trend to tell which.

Should I send more to close the gap? No. Sending more into a widening gap just grows the unopened bar and worsens fatigue. The right moves lift the open bar relative to the send bar: tighter segmentation, subject-line testing, better send timing, and pruning dormant contacts. The goal is a smaller gap, not a taller send bar.

Why might the send bar not match my Klaviyo recipient count? We may draw the send bar from delivered (net of bounces) rather than recipients (gross). If you compare against a recipients-based Klaviyo view, the bars differ by the bounced volume. Confirm which basis each view uses.

Does this include SMS? No. SMS has no open event, so it is excluded from both bars. This chart is email only.

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Tracked live in Vortex IQ Nerve Centre

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