Do you struggle to come up with great subject lines for your email campaigns?

The subject line is the start of the readers’ experience with your campaign, and, in a world of increasing distractions, it can also be the end of their experience if you don’t make it captivating and engaging.

Read on to learn 8 subject line formulas for writing a great subject line that engages your readers and gets your emails opened that you can apply to your next email marketing campaign.

8 Formulas for creating the best email subject lines for open rate and conversions.

Tweak each of these eight formulas as need to create your own customized best email subject lines for open rate and conversions.

1. The question subject line

Questions make great email subject lines because they get the reader to think about how the subject matter applies to their own life.

The best subject lines will resonate with the reader and their past experiences, while arousing a sense of curiosity to learn more about the subject and whether their experiences are similar to others.

For example:

• Do you check your emails when you first wake up in the morning?
• Are you a zombie without your morning coffee as well?

These subjects lines work because the reader can relate to these behaviors, but are also drawn to click-through to possibly learn more about whether others have similar experiences and what the possible implications of that behavior is.

2. The ‘How to’ subject line

The “How to” subject line formula works so well because it forces you to describe the content of the email in very clear language. Take these 3 subject lines, for example:

• How to get better marketing results through beautiful design
• How to win friends and influence people
• How to get 1,000 new email subscribers in 1 day

By reading these subject lines, you know exactly what you are going to learn from opening the email.

The key to success with this subject line formula is focusing on the benefit. Nobody actually wants to learn another process or methodology. Instead, they want to get the end benefits of better marketing results or new email subscribers, so make sure, when using a “How to” subject line, that you focus on the benefits and not the process itself.

3. The scarcity subject line

Scarcity is a powerful driver of human behavior. When something is in short supply, our fear of missing out kicks in and we are compelled to act.

Adding a time or availability limitation encourages readers to open and act on your email before it’s too late. For example:

• Only 2 days left to get 50% off shoes
• Hurry! Only 3 consultation spots left.
• Get free shipping if you order within the next hour

The key to using scarcity in your email subject lines is importance. If the reader doesn’t have any intention of purchasing from you, they are not going to care that they can get free shipping if they purchase in the next hour. You need to make sure the offer you are presenting is important to the reader before you bring scarcity into it to try to compel them to act quickly. Otherwise, the time or availability limitation you are imposing is irrelevant to them.

4. The announcement subject line

Using words like “Introducing” and “New” in your email subject line gives the reader a feeling that your email contains new, breaking information they haven’t heard yet.

In our recent study on power words in email subject lines, we found that email subject lines that included terms like “Introducing” and “New” increased the chance of the email being opened by 9.45% and 3.26%, respectively.

Examples of this formula in action include:

• Introducing Canvas: A better way to send emails
• Update to our iPhone App
• See our new design gallery

By using words like “Introducing” and “New” in the subject line, you are letting people know that your email contains new information they don’t know yet and are encouraging them to open the email and learn more.

5. The number subject line

The best subject lines for open rates set people’s expectations and provide a structure for the content of your email.

Every time we A/B test our blog post headlines, we find that the version of the headline containing the number outperforms the one that doesn’t. For example, when we A/B tested “3 steps to measuring the success of your email marketing with Google Analytics” against “How to measure the success of your email marketing with Google Analytics,” the subject line with a number got a 57% increase in opens.

So, wherever possible, use numbers to make your subject line more specific. For example:

• 30 ways to build your email list
• 3 steps to sending beautiful email campaigns with Canvas
• 10 product announcement emails reviewed for conversion

The key to success with this formula is the number you use. If you are suggesting effort a reader needs to expend (like steps in a process for instance), then using a low number works better, as it suggests the process is quicker and easier. However, if you are providing value to the reader (like a number of ways to increase email subscribers), then a higher number will work better, as it increases the reader’s perception of the value your email will provide them.

6. The curiosity gap subject line

Viral websites like Buzzfeed have built publishing empires off the back of a psychological phenomenon known as the curiosity gap.

Professor George Loewenstein coined this term to describe the gap between what we know and what we want to know. When we notice a gap in our knowledge, it produces a feeling of deprivation that prompts us to go looking for that piece of missing information in order to stop feeling deprived.

However, curiosity requires a little bit of initial knowledge first. We’re not curious about something we know absolutely nothing about. However, as soon as we know even a little bit, our curiosity is piqued and we want to learn more.

The best subject lines for open rates leave a small curiosity gap. For example:

• Dave Richardson asks the most basic question ever, and stumps our smartest politicians
• This little-known copywriting trick will increase your email click-through rate
• 9 out of 10 Americans are completely wrong about this fact

As you can see, these subject lines leave just enough information out to pique your curiosity. What is the question Dave asked? What’s the fact that 9 out of 10 Americans are wrong about? By piquing people’s curiosity, you provoke the sense of deprivation and compel them to open the email to learn more.

7. The surprise subject line

Everybody loves play-on words and a pleasant surprise. In fact, studies on brain activity show that these unexpected occurrences light up the pleasure centers of the brain.

Whether it’s a small chuckle or an unexpected offer that benefits the user, using surprise in your subject line causes the reader to pause while scanning through their inbox and piques their curiosity enough to open the email and learn more.

Some examples include:

• Warning: Unattended items in your shopping cart may be eaten by gnomes
• What Elvis Presley can teach you about email marketing

The key here is not so much to use a specific formula, but just to surprise the reader with something they wouldn’t expect.

In fact, during Barack Obama’s presidential election campaign his team used the subject line “Join me for dinner?” in one of their email campaigns. While “Join me for Dinner” is certainly not a surprising subject line, the fact that it came from the President of the United States certainly surprised a few people.

8. The personalized subject line

Working your subscriber’s name into the subject line of your email adds a personal touch that is likely to catch your reader’s eye. Any time you can make your reader feel like you’re connecting with them on a very personal level, it builds a sense of sincerity.

In fact, in our recent study on power words in subject lines, we found that using the recipient’s first name in the subject line increased the chance of the email being opened by 14.68%.

This can be combined with some of the other formulas for maximum impact. For example:

• John, are you a zombie without your morning coffee as well?
• John, 9 out of 10 Americans are completely wrong about this fact.
• John, there’s only 2 days left to get 50% off boots.

By including the subscriber’s first name, you create a feeling that you are speaking directly to them and give your email a sense of relevancy that encourages them to open it and consume the content.

How do I write a good subject line? Email subject line best practices

Remember that technology, marketing, and conversational trends change over time. The dynamic quality of both human nature and advertising means that email subject line best practices will continuously evolve. Here’s what you should keep in mind when writing the best subject lines for open rates today.

Segment your audience.

There’s no reason to send the same generic subject line to your entire list. Instead, break your list up based on different demographics or behavior to create the best email subject lines for an open rate of unique groups.

Get personal.

People expect personalized content. Beyond using each subscriber’s name, the best subject lines for open rates are crafted using unique information you’ve collected about locations or interests.

Be specific, yet concise.

Which email are you more likely to open?

• Yum, mac and cheese

OR

• Yum, bacon and white truffle mac and cheese

People don’t have time to wonder if your email’s copy might interest them. Let them know what’s inside right away by getting specific with your subject line.

Use actionable language.

Make it clear from the get-go how your readers to take action. What do you want them to do? Eat, shop, donate, wear, relax, listen? Use verbs that help the reader visualize themselves taking action with your service or product. Just make sure to avoid spam words.

Send them at the right time.

A subject line about happy hour specials probably won’t do much good on a Tuesday morning when readers will have forgotten about it by noon. Instead, the best email subject lines for open rate will be customized based on the subscriber’s state of mind when they receive the email.

How long should email subject lines be?

Subject lines should be as short as possible, while still getting your message across. It helps to know which email clients your subscribers use. Mobile apps like Gmail will generally cut off anything after 40 characters unless the reader drags the notification down to expand the info.

How do you write a subject line for a newsletter? 5 Examples for inspiration

Here are five examples of stellar subject lines for open rates we found in our inbox this week.

The Fix Chiropractic could have written it as a statement, but the question entices the reader to open. Notice they carefully wrote the preview text as a follow up to the subject line.

This subject line from The Nation Travels gets the reader thinking about traveling (action verb). The preview builds suspense with interesting destinations like Iran and a surprise location.

This timely message from Ancestry about Irish heritage was sent out on St. Patrick’s Day.

UNICEF always writes email subject lines that create urgency. This subject line contains the action verb “tell” and a hashtag to encourage virtual action as well.

This subject line from QuickBooks is personalized based on the subscriber’s employment. Plus, who doesn’t like free stuff?

Wrap Up

Your subject line is what entices your reader to open your email and pursue the information inside, so it’s important to put some serious thought into this portion of the writing process.

There are many ways to write an interesting, compelling subject line based around the few tips we’ve provided here. They key is to A/B test different types of subject lines to see which ones work best for your unique audience, as it all comes down to what your audience is looking for in the emails they receive from you.