The complete measurement system for email newsletters — what to track, exact formulas, benchmarks by list size, and the weekly 20-minute routine that catches problems before they cost you revenue.
Most newsletter creators track the wrong things. They watch subscriber count climb, celebrate opens that Apple's mail app faked on their behalf, and have no idea whether their list actually generates revenue. The result is a newsletter that looks healthy for two years and then dies overnight when they try to monetize it.
The fix is simple: track exactly seven newsletter metrics, know the formula behind each one, and compare against realistic benchmarks for your list size. This guide gives you all three — plus a diagnostic table that turns a bad number into a fix, and a worked example with real arithmetic you can copy into your own spreadsheet today.
Seven: open rate, click-through rate, click-to-open rate, list growth rate, unsubscribe/churn rate, revenue per subscriber, and spam complaint rate. They cover the full funnel — delivery, engagement, growth, and money — and every other metric rolls up under one of them.
35–45% for lists under 5,000; 25–35% for larger lists. But opens are inflated by Apple Mail Privacy Protection, so treat open rate as directional and judge health by CTR instead.
2–5% of delivered emails for small lists, 1–2.5% above 50,000 subscribers. Mailchimp's 2025 industry benchmarks run 1.9–3.4% CTR. Clicks can't be faked, which makes CTR the most reliable engagement metric.
Unique clicks ÷ unique opens. A good CTOR is 8–15%. It isolates content quality from subject-line quality: high opens + CTOR under 5% means your subject lines are overselling the body.
(Net new subscribers this month ÷ starting subscribers) × 100. Example: 3,890 start, +210 new, −58 lost = 152 net adds = 3.9% monthly growth. Healthy is 3–7%/month for small lists.
$1–5 per subscriber per month for a well-monetized list. Below $0.50/subscriber signals a monetization-mechanics problem (too few offers, no welcome sequence), not a list-size problem.
A structured spreadsheet with one row per issue and one row per month, with formulas doing the math. The Newsletter Metrics Tracker ($11, one-time) is a ready-built 8-tab version with auto-calculated metrics, list-size benchmarks, and a self-audit.
Every email platform ships a dashboard with 15+ numbers. Seven of them actually drive decisions. Here is the complete list, with the formula and healthy range for each:
| # | Metric | Formula | Healthy range | What it tells you |
|---|---|---|---|---|
| 1 | Open rate | Unique opens ÷ delivered | 35–45% small lists | Subject line + sender reputation (inflated by Apple MPP — directional only) |
| 2 | Click-through rate | Unique clicks ÷ delivered | 2–5% small lists | The most reliable engagement signal; immune to MPP |
| 3 | Click-to-open rate | Unique clicks ÷ unique opens | 8–15% | Content quality isolated from subject-line quality |
| 4 | List growth rate | (End − start − gross adds…) ÷ start | 3–7%/mo small lists | Signup pipeline health |
| 5 | Churn / unsub rate | Lost subscribers ÷ delivered (per send) or ÷ list (per month) | <0.5% per send | Whether content matches what readers signed up for |
| 6 | Revenue per subscriber | Monthly newsletter revenue ÷ average list size | $1–5/sub/mo | Whether the newsletter is a business or a hobby |
| 7 | Spam complaint rate | Spam complaints ÷ delivered | <0.1% (hard ceiling 0.3%) | Deliverability survival — the metric that can get you banned |
What you can safely ignore or check only occasionally: total subscriber count (vanity — the components matter more), open-to-click ratio (it's just CTOR inverted), read time, forwards and shares (nice, not actionable), heatmaps (only when redesigning), bounces (watch until <2%, then ignore), and social share counts.
Open rate measures how many delivered emails registered an open. It used to be the headline email metric; since Apple Mail Privacy Protection arrived, it's the least trustworthy number on your dashboard. Keep tracking it — trends are still meaningful — but never make a decision from open rate alone.
CTR is unique clicks divided by delivered emails. A click requires a human to read something and act, so it can't be manufactured by a mail client prefetching images. When your ESP's dashboard shows one number, make it this one.
CTOR answers a narrower question: of the people who opened, how many found something worth clicking? That makes it the best single measure of whether your actual content delivers on the subject line's promise. It also conveniently cancels out MPP noise inside a single issue (inflated opens deflate CTOR — if both open rate and CTOR look great, your content genuinely works).
Growth rate tells you whether your signup machine is running. Raw subscriber count tells you nothing: 20,000 subscribers growing at 0% per month is a dying list with a nice screenshot; 800 subscribers growing 8% monthly doubles in nine months and typically has 10x the engagement rate.
A few unsubscribes per send are healthy — it means your list is self-selecting. What you're watching for is the trend: a doubling of your baseline unsubscribe rate after a content change is the clearest signal readers have that something broke the promise they subscribed to.
Divide total monthly newsletter revenue by average list size. This single number tells you whether you have a monetizable asset. It also stops you from chasing growth that costs money: a list earning $0.05/subscriber/month at 50,000 subscribers earns $2,500/month — a list earning $3/subscriber/month at 5,000 subscribers earns $15,000/month.
Google and Yahoo's 2024 bulk-sender rules made this the one metric that can kill your newsletter outright: consistently above 0.3% complaints and your mail starts landing in spam everywhere, for everyone. Keep it under 0.1%. Two practical fixes: send from a subdomain, and make unsubscribing one click (hiding the unsubscribe link converts unsubscribes into spam complaints).
Since iOS 15 (and expanded since), Apple Mail Privacy Protection pre-fetches every email's images through Apple's proxy servers — whether or not the human ever opens the email. The result: your ESP logs an "open" the moment the message arrives in an Apple Mail inbox. Industry analyses estimate MPP inflates reported open rates by 40% or more for lists with heavy Apple readership (iPhone and Mac users skew heavily toward Apple Mail).
Definitive answer: open rate can no longer be trusted as a measurement — treat it as directional. The most reliable engagement metrics for a newsletter in 2026 are click-through rate and reply rate, because a click cannot be faked by a mail client.
Three practical consequences:
Benchmarks only mean something against lists like yours. Small lists get inflated engagement (friends, early fans, hand-recruited readers); large lists get diluted by casual subscribers. These directional ranges reflect 2025 Mailchimp benchmark data (35–45% average open rates, 1.9–3.4% average CTR depending on industry) adjusted for list-size effects:
| List size | Open rate | CTR | CTOR | Monthly growth | Monthly churn | Rev/sub/month |
|---|---|---|---|---|---|---|
| Under 500 | 45–55% | 3–6% | 10–20% | 5–10% achievable | Under 2% | $1–5+ |
| 500–5,000 | 35–45% | 2–5% | 8–15% | 3–7% | 1–2% | $1–3 |
| 5,000–50,000 | 25–40% | 1.5–3.5% | 8–12% | 2–5% | 1.5–2.5% | $0.50–2 |
| 50,000+ | 20–30% | 1–2.5% | 6–10% | 1–3% | 2–3% | $0.20–1 |
Read the table in one of two directions:
Here's a single real issue, worked end to end. Copy this structure into a spreadsheet and you have 80% of a working metrics system.
Issue #17 — the raw numbers: 4,200 sent → 200 bounces/failed → 4,000 delivered. Unique opens: 1,880. Unique clicks: 128. Unsubscribes: 6. Spam complaints: 2. Newsletter revenue attributed this month: $1,140 (average list size 4,042).
Open rate = unique opens ÷ delivered = 1,880 ÷ 4,000 = 47.0%. Note the divisor is delivered, not sent — always divide by delivered; bounces aren't people who chose not to open.
Click-through rate = unique clicks ÷ delivered = 128 ÷ 4,000 = 3.2%. Use unique clicks (a person, not an action) — most ESPs default to unique, but check, because total clicks can double-count the same enthusiastic reader.
Click-to-open rate = unique clicks ÷ unique opens = 128 ÷ 1,880 = 6.8%. Slightly below the 8% healthy band → the content under-delivered on the subject line's promise. Not a crisis; a note for next issue.
Unsubscribe rate = unsubscribes ÷ delivered = 6 ÷ 4,000 = 0.15%. Comfortably under the 0.5% per-send ceiling.
Spam complaint rate = complaints ÷ delivered = 2 ÷ 4,000 = 0.05%. Under the 0.1% target with room to spare.
Revenue per subscriber = monthly revenue ÷ average list size = $1,140 ÷ 4,042 = $0.28 per subscriber per month. Below the $1 target → the monetization mechanics (offer count, welcome sequence, promotion cadence) are the constraint, not the list size.
Per-issue metrics measure today; the subscriber ledger measures trajectory. Track four numbers per month and growth becomes mechanical:
| Month | Start | New | Lost | End | Net adds | Growth % | Churn % |
|---|---|---|---|---|---|---|---|
| June | 3,610 | 190 | 52 | 3,748 | +138 | 3.8% | 1.4% |
| July | 3,748 | 205 | 55 | 3,898 | +150 | 4.0% | 1.5% |
| August | 3,898 | 198 | 54 | 4,042 | +144 | 3.7% | 1.4% |
Formulas: net adds = new − lost. Growth % = net adds ÷ start. Churn % = lost ÷ start. The August row: 198 − 54 = 144 net adds; 144 ÷ 3,898 = 3.7% growth; 54 ÷ 3,898 = 1.4% churn.
Two patterns to watch for in this ledger:
The compounding payoff: a list growing 5%/month with stable engagement roughly doubles in 14 months. That's the entire growth strategy for most solo newsletters — hold engagement flat, hold growth rate flat, let the math work.
Every other metric exists to protect this one. Revenue per subscriber (monthly revenue ÷ average list size) turns your newsletter from a popularity contest into an asset with a valuation — newsletter businesses are commonly valued at a multiple of revenue, and a list monetizing at $2–5/subscriber/month is sellable at sizes where a $0.10/subscriber list is not.
Practical targets by stage:
And the diagnostic use: if growth is strong, engagement is strong, and revenue per subscriber is still under $0.50, you have a monetization design problem. More subscribers will not fix it. Fewer, better offers will.
The whole point of tracking metrics is turning a bad number into a specific action. This table is the compressed version of a hundred hours of newsletter troubleshooting:
| Symptom | Most likely cause | Fix |
|---|---|---|
| Open rate fine, CTR low | Content doesn't deliver on the subject line | One clear clickable idea per issue; put the link early; cut to one CTA |
| Opens and CTR both falling | Deliverability decay (reputation, list age) | Check spam placement with a seed test; warm up sending; prune 90-day zero-clickers |
| CTOR great, CTR terrible | Subject lines underselling | Rewrite subject lines to match the best content (see the copywriting swipe file for 101 proven patterns) |
| CTR fine, unsubscribes doubled | Content or cadence shifted away from the subscription promise | Return to the promise made at signup; survey unsubscribes for one week |
| Growth under 2%/mo, everything else healthy | No signup pipeline | Lead magnet + signup forms in high-traffic spots; cross-promo with 2–3 similar lists |
| High signups, high churn | Wrong audience or no welcome sequence | 5-email welcome sequence; re-permission the list; fix traffic sources |
| Engagement great, revenue ≈ $0 | No offer architecture | Add one own-product offer + one affiliate; 3:1 value-to-promo ratio |
| Complaints over 0.1% | List quality or unclear consent | Double opt-in; one-click unsubscribe; audit how addresses were collected |
Metrics only matter if someone looks at them on a schedule. This routine takes 20 minutes per week and is the difference between a dashboard you glance at and a system that runs your newsletter:
Your ESP's dashboard shows the current issue's numbers but makes three things nearly impossible: seeing trends across 40 issues side by side, connecting subscriber growth to revenue in one view, and benchmarking yourself against your list-size band. That's a spreadsheet problem, not a software problem.
The minimum viable system is three sheets:
Building that from scratch takes an evening and works fine. The pre-built option is the Newsletter Metrics Tracker — an 8-tab Excel template designed around exactly this system:
The Newsletter Metrics Tracker is an 8-tab Excel template that auto-calculates every metric in this guide — open rate, CTR, CTOR, growth, churn, and revenue per subscriber — benchmarks you by list size, and includes the 20-point self-audit. One-time $11, no subscription, works in Excel, Google Sheets, and LibreOffice.
Get the Newsletter Metrics Tracker →The seven metrics, the benchmarks by list size, the diagnostic table, and the weekly review — that's the entire measurement system for a solo newsletter. It fits in one spreadsheet, takes 20 minutes a week, and answers the only three questions that matter: is the list growing, is it engaging, and is it earning?
If you're earlier in the journey, start with the how to start a newsletter guide (30-day launch plan) and the email list monetization guide (the $1–5/subscriber math). For making each issue look professional without design work, the newsletter HTML templates give you 20 ready-to-send layouts. And once your metrics are humming, the small business KPI dashboard extends the same discipline to the rest of your business.
Measure the seven. Review weekly. Fix one thing at a time. That's the whole game.