Math Clocks
& Other Interesting Clocks

Our math clocks have been selected by
at for its online store
in New York for its museum shop
in London for its holiday gift guide
in Pasadena for its campus bookstore


New in December 2021: SB Crafts has a new collection of JRMF clocks, each featuring a design based on a popular math activity from the Julia Robinson Mathematics Festival.  All the general info below applies to them but they are described on their own page - click here to see it. -->


Note: Clicking on a picture of a clock
opens a new window containing a larger
picture of that clock, so that you can
see it and read about it simultaneously.


Purchasing & General
information below



The Math Clock – Student Edition & Engineers Edition

In place of the standard numbers 1 to 12, this clock displays an interesting assortment of expressions from many different areas of curriculum and recreational mathematics, which of course evaluate to the numbers 1 to 12. The student edition comes with a small green card that provides a couple of conceptual words for each expression – to facilitate the student looking up the concepts on the Internet. The engineers edition is labeled as such, so is appropriate for non-students.

Particularly well-
suited for engineers and high schoolers.

The Math Clock – Professional Edition

A more advanced version of the previous clock, this is our flagship product! The most advanced expressions involve calculus and number theory. (No hint card is included but our email address is on the back in case you have any questions!)

For professional mathematicians,
math aficionados,
or mathematically inclined college students.

The Math Clock – Radian Edition

In polar coordinates, angles are measured counter-clockwise from the positive x-axis. Thus, this clock starts at midnight with both hands pointing to what is normally the 3 o'clock position – and then from there it goes backwards!
A full circle is 2π radians, so each hour is 2π /12 = π / 6 radians. To facilitate time-telling, the unreduced terms' numerators, which indicate the hours, are written in green.
The squiggly second hand represents a sine wave.
Sorry, this clock is currently unavailable. Email to be notified when it becomes available.

Prerequisite - a
course in Algebra 2
or Unit Circle Trigonometry!

The Math Clock – Radian Edition – Version Tau

This clock has all the special features of the previous clock: direction of motion; orientation of hours; sinusoidal second hand; green cheat marks; and extra time.
However, here the radian measures are expressed in terms of τ, the true circle constant, rather than . (See TheTau Manifesto.) A full circle is τ radians, so each hour is τ /12 radians. The central image includes a Tao symbol. Designed on Tau Day, 2011.

Especially for
τ aficionados.

The Math Clock – Prime Edition

Prime numbers are printed in red. For composite numbers, their prime decomposition is shown. Since the number 1 is neither prime nor composite, which is an important and often-misunderstood fact, it is printed specially, as an outline. The second hand is red.

Recommended for grades 4 to 8, especially for upper elementary or middle school classrooms.

The Math Clock – Primorial Edition

With the same color scheme as the previous clock, this advanced version uses several different concepts from prime number theory – prime counting functions, twin primes, Mersenne primes, Lucas primes, Fermat primes and primorial primes.

Recommended for graduate student or professional number theorists .

The Math Clock –
Perfect Edition

A natural number is called deficient, abundant, or perfect, depending on whether the sum of its proper factors is less than, greater than, or equal to the number itself. Most are deficient. Abundant ones, such as 12, 24 and 60, are used for measuring time, so we can divide it up lots of different ways. Scarcely any are perfect. The first four were known in 300 BCE, but the 49th, which is ≈ 45 million digits long, was just discovered in January 2016, the month this clock was created. It shows the first 12 perfect numbers, in terms of the corresponding Mersenne primes, whose index is in red. No one knows how many perfect numbers there are.

Another perfect clock for number theorists
or general number aficionados.

The Math Clock –
Pi Edition

This clock was created especially for Pi Day but it works just as well the rest of the year. The expressions involve many different uses of π as a mathematical symbol, not just for the well-known transcendental number but for more obscure ideas in branches of mathematics from number theory to algebraic topology.
(Thus, this is a perfect horizon-expanding gift for those geeks who have been wasting their extra brain cells competing to memorize the longest sequence of digits constituting 0% of π's decimal expansion!)
The colorful design in the center is, of course, a pie chart.

Our most advanced clock, especially appealing to π aficionados.

The Math Clock –
Sets Edition

The colorful design in the center of this clock is a Venn diagram that makes use of the additive colors of computer graphics. Thus the main sets are the primary RGB colors, their binary intersections are the corresponding secondary CMY colors, and the intersection of all of them is white.
The 12 elements of this universe are placed to simultaneously maximize aesthetics and pedagogy, illustrating many different elementary set theory concepts (unions, intersections, complements, set differences, symmetric differences, combining set operations, and cardinality).

For set aficionados and mathematics classrooms.

The Math Clock –
Figurate Edition

The nth hour is represented by the nth triangular number, the nth square number and the nth centered hexagonal number. To easily distinguish them, each type of figurate number is colored to match the corresponding figure in the center.
Also included in the central picture are recurrence relations, closed-form expressions, and relationships between the three different sequences

Since this clock involves formulas, it
is appropriate for
ages T4 to S10, like
the Fibonacci Formula clock.
Photo available in early November

The Math Clock –
1-2-3 Edition

In our newest clock, the expression for each hour is composed of the numerals 1,2 and 3, in that order. No other numbers, just operators and functions, are used.

The central picture shows a 30°-60°-90° triangle, because of its irrespective but mnemonic side length ratios of "one, two, root three".

Appropriate for ages
1x2x3 to123.

The Math Clock –
Recursive Edition

Whether you start reading the circular saying at the top or bottom of the clock, the circular meaning is the same.
The text is colored in spectral order, somewhat like a double rainbow.
The successor function, an important primitive recursive function, is applied to 1 n-1 times for the nth hour.

For fundamental number theorists, theoretical computer scientists, and metamathematicians.

The Math Clock – Fibonacci Sequence

In this clock, the hours are represented by the corresponding number in the famous Fibonacci sequence, which is 1,1,2,3,5,8,... The nth term in the sequence, Fn, represents hour n on the clock.
The rabbit motif highlights the well-known origin of the Fibonacci sequence as a rabbit population model. The design is based on an ancient puzzle called the three hares. (It's a simple Sam Lloyd type puzzle: how many ears are there if each of the 3 hares has 2 ears?)
The hour and minute hands are shaped like rabbit ears.

Appropriate for ages
8 to 89, especially
for Fibonacci aficionados.

The Math Clock – Fibonacci Formula

See the previous clock's description regarding the design in the center and the clock hands. In this variation, the hours are represented by arithmetic expressions involving the terms of the Fibonacci sequence (i.e. F1=1, F2=1, F3=2, F4=3, F5=5, etc.) Students who are unfamiliar with the Fibonacci sequence can actually derive it by using simple algebra to combine the expressions and solve for the terms, and then deduce the pattern.

Appropriate for
ages 10 to 100.

The Math Clock – Binary Edition

This clock, a more colorful and more durable version of our binary CD clock, was created to coordinate with our binary wrapping paper. The numerals are a neon-like green, reminiscent of antediluvian computer screens, 'though not as bright as the paper or t-shirt. The text in the center is written in ASCII code and is as descriptive as that of the wrapping paper. Note that this clock does not have a second hand – after all, there are already too many digits in binary times!

For computer geeks
of ages 10102
to 11001002.

The Math Clock – Hex Edition

This is the same as the previous clock (despite the poor photo quality) except that it uses base 16 instead of base 2, with a typical computer programming language notation for hexadecimal numbers, and it has a barely visible black second hand.
For computer geeks
of ages 0xA
to 0x64.

The Rubik's Clock - Solution Edition

As the hours go from one to twelve, the cube gets solved in 11 stages, each of which involves just one or two turns.  The steps' instructions are printed lightly on the clock face's inner circle in a standard code, which is explained in detail on the back of the clock. The images and instructions are from Tom Davis.
For Rubik's Cube aficionados who
care about time.

The Rubik's Clock –
Design Edition

This is the same as the previous clock except that it goes in the other direction - from a solved cube to the mountain "peak" design, with the accompanying instructions reversed, of course. Apparently some people who can solve the cube like to spend time creating designs rather than just speed up their solving time. 
For artistic Rubik's
Cube aficionados.

The Math Clock – Metric Edition

A great gift for people who are constantly trying to promote the metric system in the US. While we support their hopeless cause, at least for distance and mass, 12 and 60 are far better choices for dividing time into, because they are both abundant and superior highly composite numbers. Decidays are indicated with thick ticks marks, and centidays with thin tick marks, around the outer edge. Since the clock movement is not metric, on most decidays, the centiday hand will not be pointing straight up 5 o'clock and 10 o'clock are beautiful exceptions. On the other hand, that means this clock is still useful for people old enough to tell time from the hands' angles. No second hand is included, since it could be disconcerting to hear a tick every 23 microdays.
For metric
proponents of
ages 10 to 100.

_    _    _    _    _    This is the dividing line between the math clocks and the non-math clocks,   _    _    _    _    _
although we admit that there's some mathematical flavor in virtually all of our clocks.


Corona Time
– The Covid Clock

The 12-word sentence marking the hours expresses why you don't need this great time piece conversation piece. 
Note that these clocks don't actually tell time - they may be fast, slow, floppy or stagnant. Thus we are selling them at cost, i.e. 50% off, during the pandemic. Any amount you choose to pay above cost will be donated to a local Covid relief fund. A working version may be available upon request. There's no second hand since we think silence is more important than the semblance of precision these days.  

For anyone who doesn't have an "essential" job.

The Chemistry Clock

The hours are represented by the atomic numbers of elements, namely the first 12 elements of the periodic table. Different background colors correspond to different kinds of elements, such as alkali metals and noble gases. A colorful key on the back of the clock explains the types of elements as well as all the other symbols from the periodic table.
The canonical image of electron rings in the center matches the hours chromatically and the clock hands thematically.

Appropriate for ages 10 to 100, and
science classrooms.

T-Time –
The Ortho Clock & the Chiro Clock

This is our first personalized clock. The name of the doctor or the practice is written along circular arcs in the center.
Its design was inspired by an accident; at the doctor's office, we learned that humans have exactly 12 thoracic vertebrae, and they're called T1 through T12.
The nth hour is represented by a superior view of the nth thoracic vertebra, with the label Tn. And the ornate clock hands complement these graphics.
(As with our Student/Engineer editions, the Ortho/Chiro editions are distinguished on the labels.)

Intended for the medical offices of general or spinal orthopedic surgeons and chiropractors.

The Dental Clock

Our second personalized clock was created to make a small dent in our huge dental bills. The name of the doctor or the practice is written along circular arcs in the center. The nth hour is represented by a facial (i.e. buccal or labial) view of permanent tooth #n (according to the ADA's Universal Numbering System, starting with the furthest back upper right molar). The hour and minute hands are evocative and the second hand is playful.

Intended for the medical offices of general dentists, orthodontists or oral surgeons.

The Music Clock

This geometric arrangement known as the Circle of Fifths is perfect for a clock!
The hours are represented by the # (i.e. number) of #s (i.e. sharps) in the key signature. (Note that when no sharps appear, the number of sharps equals 12 minus the number of flats.)
The label on the back explains how the design is used for composing Western music and also lists the 12 major and corresponding minor keys.
And the highly ornate hands complement the treble clefs.

For musicians of all type and especially for composers and music teachers.

Carb Clock

Each hour is represented by a cross-section of a piece of fruit that has that number of grams of carbohydrate per piece, to the nearest gram. For example, an avocado contains only 2 grams of carbs! (Note that the amount can vary depending on the size of the piece of fruit, so do not rely on this carb counter for your diet.)

Appropriate for weights of 100
to 300.

Hebrew Clock

In Hebrew, the letters of the alphabet have numerical values, which are used to represent the hours on this clock (e.g. alef is 1, yud is 10, yud-alef is 11). The ornate style of the hands matches the calligraphic font.

Appropriate for ages
5 to 500,
and Hebrew school classrooms.

Hebrew Clock – Reverse Version

Since Hebrew is read from right to left, just for fun this clock runs backwards! It looks particularly nice when placed side-by-side with the previous one, as they're then mirror images. Sorry, this clock is currently unavailable. Email to be notified when it becomes available.

Appropriate for ages 500 to 5.

Hindi Clock

Contrary to popular belief in the West, the Arabs were not the first to use a positional decimal numeral system – they learned it from the Indians (who may have learned it from the Chinese). The numerals on this clock are the Indian ones in their modern Devanagari form.
The clock's coloration and central design reflect those of the flag of India. In fact, the 24 spokes of the Ashoka Chakra represent the 24 hours of the day.

For aficionados of India and/or
history of science.

Portraits Clock

Our most personalized clock is appropriate as a Bat Mitzvah gift with portraits from the ages 1-12, or a first birthday gift with monthly photos, or a high school graduation gift with portraits from the grades 1-12, or a Mother's Day gift for a woman with 12 grandchildren, or . . . The gold-hued hands feature diamonds and a heart, connoting preciousness and love. Both the wording and the rim color are somewhat customizable.

For special people
on special occasions.

General description:

All models come in a 10"(25cm)-diameter size, suitable for homes and offices.
The black-rimmed ones are also available in a 14"(35cm)-diameter size – which is
almost twice as large! – suitable for classrooms and studios.
Each clock has metal hands, not plastic, and a U.S.-made I-shaft movement (except for
the reverse movements, which are from Asia); and requires one AA battery, not included.

Prices:  All 10" clocks cost $40 except for the following:

  • the prime and primorial versions, which are priced at P13 ($41) and P14 ($43), respectively
  • the Fibonacci versions, which cost F9 ($34)
  • the pi clock, which is priced at   14 π dollars ($44)
  • the 1-2-3 version, which costs $12x3 ($36)
  • the binary clock, which costs $1010102 ($42),
    and the hex clock, which is only $2916
  • the Hebrew clock, which is priced at double-chai ($36)
  • the ones that run backwards, which cost $120
  • the personalized business ones, which cost $75 (but are probably tax-deductible)
  • the JRMF ones, which cost $50 (and are partly tax-deductible)
  • the portraits clock, which is priceless (but please inquire anyway!)

    The 14" clocks cost an additional $20.

    California residents must add sales tax.

Shipping Click here for new, fairer shipping cost tables
                 Please note that deliveries outside the U.S. may be subject to customs duties, taxes
                 and/or fees upon arrival; these costs are not included in our product or shipping charges.

Buying a Gift? Mathematical wrapping paper is $4.

Can't Decide Which Clock to Buy? Cute gift certificates are also available.
                                                                  (Even by email for last-minute gifts.)


To order
by check, send to SB Crafts at 6167 La Goleta Road, Santa Barbara, CA 93117.
Be sure to include an email address and/or phone number in case we need to contact you
If you have a PayPal account, you can send the payment to (note: not .com)


For any questions, PayPal assistance, international, wholesale or rush orders,
or call (805) 967-2270.