What is click-to-open rate (CTOR)?

CTOR = (Clicks / Opens) × 100. It measures how compelling your email body and CTA are for people who actually opened the email. A good CTOR is 10–15% for most industries. Unlike CTR (clicks/sends), CTOR isolates content quality from subject line performance.

How much does email marketing typically cost?

ESP platform costs: Mailchimp/Klaviyo/ActiveCampaign run $50–$500/month for lists of 5,000–50,000 contacts. Content creation: $300–$2,000/campaign depending on copywriting and design. Dedicated email marketing managers: $50,000–$80,000/year (or $50–$100/hour freelance). For small businesses, total monthly email marketing costs typically range $500–$3,000.

What is email list decay and how do I manage it?

Email lists decay at 20–30% annually through unsubscribes, bounces, and inactivity. To manage decay: (1) Implement a double opt-in process to build a higher-quality list from the start. (2) Run re-engagement campaigns for subscribers inactive 90+ days before removing them. (3) Clean your list quarterly — remove hard bounces immediately and soft bounces after 3 attempts. (4) Add lead magnets and content upgrades to continuously replenish the list.

What is revenue per email subscriber?

Revenue per subscriber (RPS) = Monthly Email Revenue / Total List Size. Industry benchmarks: E-commerce $0.10–$0.30 per subscriber per month; strong performers exceed $0.50. B2B SaaS: $1–$5+ per subscriber per month due to higher deal values. RPS is a leading indicator of list quality — a declining RPS signals list fatigue or deliverability problems.

What is cost per email sent?

Cost per email = Total Monthly Email Cost / Total Emails Sent. Total emails sent = List Size × Campaigns per Month. For a 10,000-person list sending 4 campaigns with $700/month total cost, cost per email = $700 / 40,000 = $0.0175. This metric helps you compare ESP pricing tiers and justify budget increases for list growth programs.

Email Marketing ROI Calculator

1

Enter List & Engagement Metrics

Enter your email list size, open rate, click-to-open rate (CTOR), and conversion rate from your ESP analytics dashboard. Use the preset chips to start with realistic benchmarks for your list type.

2

Add Revenue & Cost Inputs

Enter your average order value (AOV), monthly email platform cost, content creation cost, and how many campaigns you send per month. Include all costs — copywriting, design, and platform fees.

3

Review ROI Results

Review monthly revenue, ROI %, cost per email, and revenue per subscriber. The email funnel chart shows your campaign pipeline from sends to conversions. Alerts flag benchmarks you're under or over.

4

Compare Campaigns & Project List Health

Use the Campaign Comparison tab to benchmark two campaigns side by side. Switch to the List Health Projector to model how your unsubscribe rate affects list size over 3, 6, or 12 months — and how many new subscribers you need to break even.

Email Marketing ROI

ROI = (Monthly Revenue − Total Cost) / Total Cost × 100

Monthly Revenue is revenue per campaign × campaigns per month; Total Cost is platform cost + content creation cost. Industry benchmark is $36–$42 returned per $1 spent, or 3,600–4,200% ROI.

Email Funnel

Opens = List × Open Rate; Clicks = Opens × CTOR; Conversions = Clicks × Conv Rate

Each stage multiplies the previous by its rate. CTOR (click-to-open rate) isolates body copy effectiveness from subject line performance, making it a better creative quality signal than raw CTR.

Cost per Email & Revenue per Subscriber

Cost/Email = Total Cost / (List × Campaigns); Rev/Sub = Monthly Revenue / List Size

Cost per email helps compare ESP pricing tiers. Revenue per subscriber is the leading indicator of list quality — declining RPS often signals deliverability problems or list fatigue before ROI drops.

List Decay

Loss per Month = List Size × (1 − (1 − Unsub Rate)^Campaigns per Month)

Unsubscribes compound across campaigns. A 0.5% rate per campaign with 4 monthly sends equals roughly 2% list loss per month — meaning you need to add 2% of your list in new subscribers each month just to maintain size.

Open Rate The percentage of recipients who opened the email. Inflated since Apple's Mail Privacy Protection (MPP) pre-loads images; focus on CTOR and conversion rate for true engagement.

Click-to-Open Rate (CTOR) Clicks divided by opens. Measures how compelling your email body and CTA are for people who actually opened — isolating content quality from subject line performance.

Conversion Rate The percentage of email clicks that complete the desired action (purchase, sign-up, trial). It's a composite of email CTR × landing page conversion rate.

Average Order Value (AOV) The average revenue generated per transaction. Increasing AOV through bundles or upsells boosts email ROI without requiring more subscribers or campaigns.

Unsubscribe Rate The percentage of recipients who unsubscribe per campaign. Under 0.5% is healthy; above 0.5% signals content–audience mismatch, list fatigue, or over-sending.

Revenue per Subscriber (RPS) Monthly email revenue divided by total list size. Industry benchmark: $0.10–$0.30 for e-commerce, $1–$5+ for high-AOV B2B. A declining RPS is an early warning sign before ROI drops.

List Decay The natural shrinkage of an email list through unsubscribes, bounces, and inactivity. Typically 20–30% annually. You need to add that many new subscribers per year just to maintain list size.

ESP Email Service Provider — the platform used to send, track, and manage email campaigns. Examples: Mailchimp, Klaviyo, ActiveCampaign, HubSpot, Constant Contact.

Result

Conversions per campaign: 10,000 × 22% × 14% × 3% = 9.2. Revenue per campaign: 9.2 × $75 = $693. Monthly revenue: $2,772. Total cost: $700. ROI: ($2,772 − $700) / $700 × 100 = 296%.

Result

Conversions per campaign: 5,000 × 28% × 18% × 5% = 12.6. Revenue per campaign: $6,300. Monthly revenue: $12,600. Total cost: $1,150. ROI: 996%. Revenue per subscriber: $2.52/month.

Result

Monthly revenue: 100,000 × 18% × 12% × 2% × $120 × 8 = $41,472. Total cost: $2,000. ROI: 1,974%. Cost per email: $2,000 / 800,000 sends = $0.0025. Revenue per subscriber: $0.41/month.

Email marketing consistently delivers the highest ROI of any digital marketing channel — industry research cites $36-$42 returned per $1 spent. But those averages hide wide variation based on list quality, segmentation, and offer relevance.

The Email ROI Formula: Revenue, List Size, and Conversion

Email marketing consistently delivers the highest ROI of any digital marketing channel — industry research cites $36–$42 returned per $1 spent. But those averages hide wide variation. Understanding the drivers of email ROI lets you identify exactly where to improve. The email ROI formula starts with the funnel: List Size → Opens → Clicks → Conversions → Revenue. Each stage is a multiplicative lever. A 10% improvement in open rate compounds through every downstream stage. This is why subject line testing often has outsized impact — it directly affects the top of the funnel.

Open Rates, CTR, and Conversion Rate Benchmarks

Beyond the funnel, the cost structure matters. Email platform fees scale with list size, making cost per email a useful metric for evaluating ESP pricing tiers as you grow. Content creation costs (copywriting, design, testing) are largely fixed per campaign, meaning they get diluted as your list grows — a strong case for list growth programs. List health is the hidden lever most email marketers underweight. An unsubscribe rate of 0.5% per campaign sounds small, but 4 campaigns per month means 2% monthly list attrition — roughly 24% annually. A 10,000-person list loses 2,400 subscribers per year to churn alone. Your list health projector shows exactly how many new subscribers you need to acquire each month to maintain or grow your active list.

Improving Email ROI: Segmentation, Testing, and Deliverability

To improve email ROI without increasing budget: segment your list (targeted emails get 100% higher CTR per DMA research), improve the landing page (email conversion rate = CTR × landing page conversion rate, and landing page improvements often have more leverage than email copy), and run a re-engagement campaign to either reactivate or remove inactive subscribers before they drag down deliverability metrics.

What is a good email marketing ROI?+

Industry benchmarks cite an average email marketing ROI of $36–$42 per $1 spent (3,600–4,200%). In practice, ROI varies widely by list quality, industry, and offer type. E-commerce with high send frequency and strong segmentation can achieve 1,000–5,000%+ ROI. B2B with high-AOV products can achieve even higher ratios with smaller, more engaged lists.

What are average email open rates by industry?+

Mailchimp benchmarks: Non-profit 25.2%, Education 23.4%, Retail 18.4%, E-commerce 15–20%, B2B/SaaS 20–25%. Note that open rates have inflated since Apple's Mail Privacy Protection (MPP) in 2021 — MPP pre-loads images regardless of user action. Focus on CTOR and conversion rate as more reliable engagement signals.

What is a healthy email unsubscribe rate?+

Under 0.5% per campaign is considered healthy. Above 0.5% signals content–audience mismatch, list fatigue from over-sending, or poor list hygiene. List churn (unsubscribes + bounces + inactivity) typically runs 20–30% annually, meaning you need to grow your list by 20–30% per year just to maintain its current size.

How do I improve email conversion rate?+

Key levers: (1) Segment your list — targeted emails get 14% higher open rates and 100% higher CTR. (2) Optimize your landing page — the email conversion rate is a composite of email CTR × landing page conversion rate. (3) Personalize subject lines and body content. (4) Send at optimal times — Tuesday–Thursday mornings for B2B; weekends for B2C retail.

How many campaigns should I send per month?+

E-commerce promotional: 4–8 per month. B2B newsletters: 2–4 per month. SaaS onboarding sequences: daily for the first week, then weekly. Sending more than your audience expects without segmentation causes list fatigue. Unsubscribe rates above 0.5% per campaign are a reliable signal you're over-sending.

Email Marketing ROI Calculator

Campaign Inputs

ROI Analysis

Campaign A

Campaign B

Campaign Comparison

List Settings

List Health Projection

How to Use This Calculator

Enter List & Engagement Metrics

Add Revenue & Cost Inputs

Review ROI Results

Compare Campaigns & Project List Health

Formula & Methodology

Key Terms Explained

Real-World Examples

Email Marketing ROI: How to Measure and Improve It

The Email ROI Formula: Revenue, List Size, and Conversion

Open Rates, CTR, and Conversion Rate Benchmarks

Improving Email ROI: Segmentation, Testing, and Deliverability

Frequently Asked Questions

Email Marketing ROI Calculator

Campaign Inputs

ROI Analysis

Campaign A

Campaign B

Campaign Comparison

List Settings

List Health Projection

How to Use This Calculator

Enter List & Engagement Metrics

Add Revenue & Cost Inputs

Review ROI Results

Compare Campaigns & Project List Health

Formula & Methodology

Key Terms Explained

Real-World Examples

Email Marketing ROI: How to Measure and Improve It

The Email ROI Formula: Revenue, List Size, and Conversion

Open Rates, CTR, and Conversion Rate Benchmarks

Improving Email ROI: Segmentation, Testing, and Deliverability

Frequently Asked Questions

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