The Curiosity Box

Ruler of The Universe

$61.99 Shipping included

Pre-order · ships in December

Subscribing? The Ruler is already inside the Fall 2026 box.

About the ruler

It’s the world’s first ‘exponential barbershop ruler’ and while it may not be as big a deal as the invention of the pencil, we're incredibly proud of it. Our team noticed that a series of exponential curves could be devised so as to continuously and regularly grow apart. On a graph of such curves, there will always eventually be a transverse where each line is 1 cm away from the next. Then later on, they’ll eventually all be one INCH apart. And so on! In this way, every possible unit of distance can exist on a single ruler.

Even ad hoc units you may need when least expected (e.g. “how many of these paper-flowers-I-made is this sheet of construction paper long?”). Really big units (like light years) can only be partially represented, of course, but by placing the curves on a cylinder just right, we managed to make the whole device continuous.

Shipping

Pre-orders ship in December. Shipping is included in the price.

Curriculum templates

Grab a free curriculum template to connect your Curiosity Box with your teaching plans.

One ruler to rule them all

The name is a play on a “universal ruler”: it lets you make a unit out of almost anything smaller than itself. Our Curiosity Box team invented, designed and engineered it in-house, and as far as we know there’s nothing like it.

Why you’ll love it

Create your own units

Slide the ruler to turn almost anything into a unit: a popcorn kernel, a penny, your pinky.

Exponential curves

Curves that steadily grow apart are what make every unit fit on one ruler.

Useful conversions

Traditional and scientific units side by side: centimeters, inches, decimal inches, barleycorns, digits, the Chinese cun, the Japanese sun and the hydrogen line.

Instructions included

An in-depth guide so you can master your new measuring device.

Or get it inside your first box

The Ruler of the Universe is one of six items in the Fall 2026 box. Subscribe and it comes in your first box, with a free Camera Lucida on top.

1 year

$349.90

4 boxes, about $87 a box. Shipping included.

Starts with the Fall 2026 box
A new box every season after that
Free Camera Lucida

Choose 1 year

Best value

2 years

$599.90

8 boxes + 1 free one, about $67 a box. Shipping included.

Starts with the Fall 2026 box
A new box every season after that
Free Camera Lucida
Free extra Winter 2025 box, shipped with your first box

Winter 2025: Orrery Calendar (planet positions and moon phases), Erdapfel Coasters (a 1492 globe), Möbius Scarf (topology), InQ Blocks Puzzle and Robinson Crusoe: Desert Island Edition.

Choose 2 years

Questions

When does it ship?

Pre-orders ship in December. If you subscribe instead, the Ruler comes inside your first box, the Fall 2026 box, together with 5 more items.

Who made it?

The Curiosity Box team invented, designed and engineered it in-house.

Can schools and charters order?

Yes. Schools, charters and homeschool families can order directly on this site. If you need help with a school or program purchase, email us at orders@curiositybox.com.