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Last updated July 7, 2023

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How to Write the Caltech Supplemental Essays

Key Takeaway

Caltech's supplemental essays emphasize STEM disciplines and personal diversity. The prompts ask applicants to articulate their interest in an academic field, share STEM-related experiences, illustrate personal innovation, and delve into personal identity. Optional essays offer opportunities to share further aspects of identity and hobbies.

The California Institute of Technology, or Caltech for short, is a small but highly selective school that focuses primarily on STEM disciplines.

The Caltech supplemental essays are divided into two groups: required and optional. You’ll have five required essays to write (that’s quite a few!) and three optional essays to choose from.

Let’s start with the required essays.

Required Caltech Essays

Before you write anything, Caltech asks you to use a drop-down menu to choose an academic area that interests you. Don’t worry—this isn’t a declaration of your major. In fact, at Caltech, you don’t have to declare a major until the end of your first year.

But your first essay question revolves around the academic area you select, so choose whatever calls most to you right now.

Here’s the first prompt:

Why did you choose that area of interest? (200 words)

In this why this major or academic interest essay, you’ll want to be clear about the why behind your interest in that particular area.

Were you inspired by an experience or person? Is there a question that fascinates you? Is it related to a career goal?

In your answer, feel free to highlight any relevant accomplishments you have. For example, if you chose chemical engineering and you spent your junior year summer helping a chemistry professor with research, then bring it up!

This is also a place to draw upon any related references to Caltech itself. What about their program entices you? Are there any specific opportunities you’re interested in?

The next two questions go hand in hand. You’ve got 200 words to answer each of them. Here’s the main prompt:

At Caltech, we investigate some of the most challenging, fundamental problems in science, technology, engineering, and mathematics. Identify and describe two STEM-related experiences from your high school years, either in or out of the classroom, and tell us how and why they activated your curiosity.  What about them made you want to learn more and explore further?

STEM experience/activity #1

STEM experience/activity #2

These essays are your opportunity to highlight special projects or accomplishments that show magnitude, reach, and impact.

Because Caltech asks for STEM-related experiences or activities, you’ll need to choose something that relates to science, technology, engineering, or math. This isn’t the time to take a creative twist on the prompt (”Writing poetry was like science to me!”) because your essays will be read alongside applications from some of the best high school scientists in the world.

As you answer, don’t forget to address the three main questions of the prompt:

  1. Identify and describe the experience. It can be in or out of the classroom.

  2. Explain how it “activated your curiosity.”

  3. Explain how it made you want to learn and explore more.

Feel free to nerd out a little and go in-depth on a topic you’re passionate about. It can complement, be related to, or be completely different from your answer to prompt #1. Just think about how all of your supplemental essays will work together to form one overall narrative.

The creativity, inventiveness, and innovation of Caltech’s students, faculty, and researchers have won Nobel Prizes and put rovers on Mars, but Techers also imagine smaller scale innovations every day, from new ways to design solar cells to 3D printing dorm decor. How have you been an innovator in your own life? (250 words)

In your essay, you can take “innovator” literally or figuratively. Either way, you’ll want to balance your answer to this question with your answers to the previous two.

If you’ve literally innovated something, now’s your time to shine. Did you create an app to help your classmates study for your French final? Did you design a website for your mom’s small business or develop a code to count cars? Draw out the key points for your admissions officers, and make sure it’s clear why your innovation mattered (to you and to those around you).

Or, if you haven’t literally innovated something, you might think about innovation more metaphorically and use this prompt to show admissions officers a softer or more creative side of yourself. Maybe you innovated a new way to teach algebra to your tutee or rediscovered the design for The Apple Picker 5000 that you drew up when you were five years old. Just be sure to draw out what it all means for who you are as a technical innovator now.

The process of discovery is best advanced when people from diverse backgrounds come together to solve the greatest challenges in their fields. How do your past experiences and present-day perspectives inform who you have become and how you navigate the world? (250 words)

By this point, you’ve shown Caltech admissions officers your academic and technical side and maybe let them in on a few important stories from your life.

With this final required prompt, it’s time to dig a little deeper. This is a diversity essay.

Caltech admissions officers will know from the rest of your application why you’ll make a good scientist. Now you need to show them who you are as a person.

Feel free to write about any area of your identity that has shaped your perspectives. Also pay attention to the wording of the prompt: admissions officers want to know about your past experiences AND present-day perspectives. What’s more, they specifically want to know how they inform 1) who you’ve become, and 2) how you navigate the world.

You could write about a particular part of your upbringing, what it’s like to live in the world with a particular identity, or even an impactful experience you had that changed your perspective.

Optional Short Answer Questions

Here’s what Caltech says about the “optional” designation: “Optional. We promise.”

Take their word for it. Choosing not to answer these questions won’t automatically get your application tossed into the reject bin.

But choosing not to answer them is also a choice not to add to your cohesive application narrative. Answering the questions can give admissions officers more information to get to know you with (and therefore more data to base an admissions decision on!).

Let’s take a look at the optional prompts.

If there are aspects of your identity that you feel are not captured elsewhere in this application, please provide that information below. (150 words)

You may have covered everything you needed to cover in the last required prompt, but this prompt gives you more space if there’s something else you want to convey.

Applicants answering this prompt might choose to write about gender identity or sexuality, race or ethnicity, ability or disability, class, or general background information.

Whatever you write about, make sure there’s a clear takeaway for admissions officers.

When not surveying the stars, peering through microscopes, or running through marathons of coding, Caltech students pursue an eclectic array of interests that range from speedcubing to participating in varsity athletics to reading romance novels. What is a favorite interest or hobby and why does it bring you joy? (100 words)

The other required and optional prompts are all pretty straightforward. But this one gives you leeway to show some personality.

Note the emphasis on “joy” in the prompt. This isn’t just about a hobby that you’ve excelled at or participated in for a long time. It’s about describing something that makes you genuinely happy, even if it’s not a world-changing activity.

Think of your answer to this prompt as the sprinkles on top of your application. It’s a way to have some fun and add a little narrative diversity.

Did you have a hard time narrowing it down to just one interest or hobby? We understand – Caltech students like to stay busy, too – tell us about another hobby or interest!  (50 words)

And here you can elaborate just a little more on a secondary hobby if you’d like. Just make sure it’s actually adding valuable information to your file, otherwise admissions officers may simply skim it and move on.


And with that, you’ll have written all your Caltech supplemental essays! Remember: you have to answer the first four, but you aren’t required to write any in the last set unless you want to.

Whichever ones you write will all work towards your cohesive application narrative, so think about them each as an opportunity to advocate for your admission. Make them count.

You’ve got this!

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