Every time a product goes out of stock, you lose sales. Industry data shows that stockouts cost ecommerce brands an estimated 4-8% of annual revenue. But not all of that revenue has to disappear. Back in stock emails let you recover a significant portion of those missed sales by notifying interested customers the moment inventory returns.
Brands with well-optimized back in stock flows report conversion rates of 8-12%, making this one of the highest-converting automated emails you can build. Here is how to set it up and maximize its impact.
What Is a Back in Stock Email?
A back in stock email is an automated notification sent to customers who expressed interest in a product that was out of stock. The customer signs up for the alert (usually via a form on the product page), and when inventory is replenished, they receive an email with a direct link to purchase.
It is different from a standard promotional email because:
- The recipient has explicitly shown purchase intent
- The timing is triggered by a real event (inventory replenishment)
- Urgency is built in because the product already sold out once
This combination of intent, timing, and urgency is why back in stock emails perform so well.
Setting Up Back in Stock Emails in Klaviyo
Klaviyo has a native back in stock feature that integrates directly with Shopify, BigCommerce, and other platforms. Here is how to set it up.
Step 1: Enable Back in Stock on Your Product Pages
Add a "Notify Me When Available" button that appears when a product variant is out of stock. Klaviyo provides an embeddable signup form for this. The form collects the customer's email address and the specific product variant they want.
In Klaviyo, go to Lists & Segments > Create List and create a list specifically for back in stock subscribers. Then configure the signup form to feed into this list with the product variant data attached.
Step 2: Build the Flow
Navigate to Flows > Create Flow and select the "Back in Stock" trigger. Configure these settings:
- Trigger: Back in stock event (fires when a product variant's inventory goes from 0 to 1+)
- Filter: Only send to subscribers who signed up for that specific variant
- Inventory threshold: Set a minimum inventory level before sending (recommended: at least 10 units to avoid overselling)
- Send window: Send within 1-2 hours of restocking to maximize urgency
Step 3: Build the Email Sequence
Email 1 (Immediate): The core back in stock notification. This is the money email.
Email 2 (24 hours later): A follow-up for non-purchasers with added urgency. "Still available, but selling fast."
Email 3 (48 hours later): Final reminder. "Last chance before it sells out again."
Step 4: Configure Smart Sending
Enable smart sending to prevent subscribers from receiving back in stock emails too frequently if they have signed up for alerts on multiple products. A 24-hour smart sending window prevents inbox fatigue.
Designing High-Converting Back in Stock Emails
The design of your back in stock email should be clean, focused, and urgency-driven. This is not the place for a lengthy newsletter format.
Essential Design Elements
Hero image: A high-quality product photo should dominate the top half of the email. Show the exact variant the customer wanted (specific color, size, or style).
Clear headline: "It's Back" or "Back in Stock: [Product Name]" works better than clever or cryptic subject lines. The subscriber signed up for this notification. Deliver the news immediately.
Product details: Include the product name, price, a brief description, and the variant details (size, color). Do not make the customer guess which product this is about.
Single prominent CTA: One button. "Shop Now" or "Get Yours Before It's Gone." Make it large, high-contrast, and impossible to miss. Place it above the fold.
Urgency element: Include a stock indicator like "Only 14 left" or "Limited quantity available." If you can pull real-time inventory data into the email, even better. This is not manufactured urgency. The product genuinely sold out before.
Social proof: A star rating, review count, or a brief customer quote below the CTA adds confidence without cluttering the design.
What to Avoid
- Multiple products: Do not include other product recommendations in the primary back in stock email. Keep the focus on the item the customer requested.
- Long copy blocks: This email should be scannable in 5 seconds. The subscriber already wants this product. Get out of the way and let them buy it.
- Discount offers: Unless the product has been sitting in stock for days without converting, do not lead with a discount. The demand is already there.
Subject Lines That Drive Opens
Back in stock emails enjoy higher open rates than most automations because subscribers are waiting for them. But your subject line still needs to deliver clarity and urgency.
High-Performing Subject Lines
- "It's back: [Product Name]"
- "[Product Name] is back in stock"
- "Good news: [Product Name] is available again"
- "You asked, we restocked: [Product Name]"
- "Back in stock (limited quantity): [Product Name]"
Subject Line Tips
- Include the product name when possible
- Keep it under 50 characters for mobile visibility
- Add a preview text that reinforces urgency: "Grab yours before it sells out again"
- Avoid ALL CAPS or excessive punctuation
Expected Conversion Rates and Revenue Impact
Back in stock emails consistently rank among the top-performing automated flows. Here are benchmarks based on data from ecommerce brands:
- Open rate: 45-65% (significantly above the 20-25% average for ecommerce emails)
- Click-through rate: 10-18%
- Conversion rate: 8-12% of recipients purchase
- Revenue per recipient: $3-8 depending on average order value
Calculating Your Revenue Opportunity
If you have 500 back in stock signups per month with an average order value of $65:
- 500 signups x 55% open rate = 275 opens
- 275 opens x 15% CTR = 41 clicks
- 41 clicks x 35% landing page conversion = 14 orders
- 14 orders x $65 AOV = $910/month in recovered revenue
That is nearly $11,000 per year from a single automated flow, and the numbers scale directly with your signup volume.
Advanced Strategies
Prioritize by Demand
If a product has hundreds of back in stock signups but limited inventory, consider sending notifications in batches. Send to VIP customers and highest-engagement subscribers first, then expand to the broader list. This rewards your best customers and reduces the frustration of someone opening a "back in stock" email only to find it sold out again.
Combine with SMS
For high-demand products, send an SMS alert alongside the email. SMS open rates exceed 95%, and the immediacy of a text message means subscribers can act within seconds. In Klaviyo, you can add an SMS step to your back in stock flow that fires simultaneously with the email.
Use Back in Stock Data for Inventory Planning
Track which products generate the most back in stock signups. This data is invaluable for inventory planning. If a product consistently has 200+ signups when it goes out of stock, that signals you need to increase order quantities or adjust reorder points.
Pre-Launch Waitlists
Apply the same back in stock mechanics to new product launches. Let customers join a waitlist, then trigger a notification flow when the product goes live. This builds anticipation and concentrates launch-day demand.
Common Mistakes to Avoid
- Not having a signup form on out-of-stock pages: If a product is out of stock and there is no way to get notified, you are leaving money on the table.
- Sending too late: Back in stock emails should fire within 1-2 hours of restocking. Waiting 24 hours dramatically reduces conversion.
- No follow-up sequence: A single email captures about 60% of the potential revenue. Adding a second and third email in the flow captures the remaining 40%.
- Ignoring inventory levels: Sending 500 back in stock emails when you only have 20 units creates a bad customer experience. Set inventory thresholds.
Back in stock emails are low-effort, high-reward automations that every ecommerce brand should have running. The setup takes a few hours. The revenue recovery is ongoing.
Want us to build this for your brand? Get a free email audit at ecomcure.com
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