The Theodorus Spiral Company is part of a multi-media, multi-access creative installation.
The pursuit of the maths and patterns of the spiral is genuine.

I first learnt about the Theodorus Spiral when I was reading An Imaginary Tale: The Story of The Square Root of -1 by Paul Nahin (1998). Each hypotenuse (longest side of the triangle) or spoke is always longer than the one before as the spiral goes around, but the difference in the change of length is getting smaller and smaller. The angle between the spokes is getting smaller and smaller while the angle between the opposite and adjacent side is always a right angle.


I had been training as an artistic blacksmith since 2006 and after seeing the theodorus spiral (on page 33 of Paul’s book) I thought of the idea to make an iron shield in the shape of the spiral. My intention was that it would be a work of art rather than a practical shield. This has evolved into a sculpture titled My Painted Elephant: Part 3: Kembla’s work; called a Monument to Hypatia. The Theodorus Spiral on the Pedastal is part of that sculpture and is featured in my novella; A Perpetual Tale to be found on my website The Red Forge Publishing House.

I also began investigating the maths of the spiral. I was learning to use Matlab and began playing with some code I had written to see what happens to the spiral at a very large x. I thought it was converging into a circle but it expands even though the change in the hypotenuse gets smaller and smaller. What is the change in the circumference of the circles? Why is the difference between the winding’s gets closer and closer to pi!

I began to ponder all these plus more of the following Theodorus Spiral mathematical and data visualisation questions:

  • what is the change in the hypotenuse and the change in the change of the hypotenuse?

  • what is the change in the angles and the change in the change of the angles

  • how far does it go?

  • what about 0 < x <1 and x < 0?

  • what would a 3D model look like?

  • how many spokes in each winding?  It seems that the additional number of spokes in each winding is between 18 and 21 in a seemingly random pattern.  I have begun calling this the Theodorus Spiral Winding Pattern and I am going to start looking for this pattern in other places.



x=1000 with dots

MATLAB CODE by Keren Sutcliffe
Created by Keren Sutcliffe 2011

clear all
%finish = 16 creates the spiral that Theodorus completed
%change the value of finish to any number
total_angle=0; winding=0; finish=16;

fprintf(‘ x hyp changeinhyp chngeinchngehyp angle chngeangle X2 Y2 winding \n’);

for x=1:finish

hyp=sqrt(x+1); chngeinhyp=1/(2*sqrt(x+1));
%outside boundry

fprintf(‘%3i %10f %10f %10f %10f %10f %10f %10f %5f \n’,x,hyp,chngeinhyp,chngechngehyp,degangle,chngeangle,X,Y,winding);

figure(1) title(‘Theodorus Spiral’) axis equal; xlabel (‘x’); ylabel (‘y’); zlabel (‘z’);

hold on
plot ([0 1], [0 0],‘k’); %First spoke
plot ([0 X],[0 Y],‘k’); %spokes
plot ([Xb,X],[Yb Y],‘k’); %boundary on xy grid

 x      hyp     changeinhyp  chngeinchngehyp   angle       chngeangle       X            Y          winding    
  1     1.414214     0.353553    -0.176777    45.000000      0.250000      1.000000      1.000000   0.125000  
  2     1.732051     0.288675    -0.144338    35.264390      0.117851      0.292893      1.707107   0.222957  
  3     2.000000     0.250000    -0.125000    30.000000      0.072169     -0.692705      1.876209   0.306290  
  4     2.236068     0.223607    -0.111803    26.565051      0.050000     -1.630810      1.529856   0.380082  
  5     2.449490     0.204124    -0.102062    24.094843      0.037268     -2.314982      0.800536   0.447012  
  6     2.645751     0.188982    -0.094491    22.207654      0.029161     -2.641800     -0.144552   0.508700  
  7     2.828427     0.176777    -0.088388    20.704811      0.023623     -2.587164     -1.143058   0.566213  
  8     3.000000     0.166667    -0.083333    19.471221      0.019642     -2.183032     -2.057759   0.620300  
  9     3.162278     0.158114    -0.079057    18.434949      0.016667     -1.497113     -2.785436   0.671508  
 10     3.316625     0.150756    -0.075378    17.548401      0.014374     -0.616280     -3.258865   0.720254  
 11     3.464102     0.144338    -0.072169    16.778655      0.012563      0.366304     -3.444680   0.766861  
 12     3.605551     0.138675    -0.069338    16.102114      0.011103      1.360698     -3.338937   0.811589  
 13     3.741657     0.133631    -0.066815    15.501360      0.009905      2.286752     -2.961547   0.854648  
 14     3.872983     0.129099    -0.064550    14.963217      0.008909      3.078259     -2.350387   0.896213  
 15     4.000000     0.125000    -0.062500    14.477512      0.008069      3.685127     -1.555584   0.936428  
 16     4.123106     0.121268    -0.060634    14.036243      0.007353      4.074023     -0.634302   0.975418  

enter image description here

Pictures of Matlab Theodorus Spirals

Different variations of basic code 

Overlapping: Apparently according to Wikipedia, in 1958, Erich Teuffel proved that no two hypotenuses will ever coincide, regardless of how far the spiral is continued. I haven’t seen this proof. If it doesn’t overlap I wonder what it would look watching, from the origin, the plot of points as the spiral winds. What is that pattern and is there a formula?

Also if the Theodorus Spiral goes on into infinity and the spokes never overlap, is this significant for computer science and information storage? I mean in terms of pointers and list/arrays/stacks or ‘theodorus positioning’???

 Theodorus Spiral Trinket Matlab picture, 3D print
and inside the VOXON

3D spiral Matlab file3D spiral

Theodorus Spiral: Cup and Saucer (2015) by K E Sutcliffe: Coloured cup and saucer with inner piece (created in Matlab)
coloured cup and saucer with inner piece

3D Theodorus Spirals (2016)by K E Sutcliffe: Two spirals at right angles to each other (created in Matlab)

3D spirals

Theodorus Spiral Shields

Port Festival Spiral1

Theodorus Spiral on the Pedestal @ The Port Festival 2015

Two Brains – new Matlab Theodorus Spiral design by K E Sutcliffe (2017)

Design Mashup (2017)

More than one spiral on one figure.

The Blades (2017)Something a bit different: starting with negative numbers.


Positive and Negative FlareUp

Theodorus Spiral: Cover of The Wave and the Particle (A novel by Keren Sutcliffe)
Cover of the Wave and the Particle

Theodorus Spiral Company Merchandise Store

Two T-shirts for website


Theodorus Spiral Company Colouring In


An Imaginary Tale -cover

Wikipedia – Spiral of Theodorus

Further Reading

Spirals from Theodorus to Chaos - coverSpiral of Theodorus - coverThe Generalised Theodorus Iteration - cover

Gronau, D. The Spiral of Theodorus

Hlawka (Gleichverteilung und Quadratwurzelschnecke, Monatsh. Math., 89 (1980) 19-44)

Kociemba, H (2014) Die Wurzelspirale

Ordered distribution of natural numbers

Theaetetus by Plato


Theodorus of Cyrene in World Cat

The Red Forge Publishing House

home of A Perpetual Tale
by Keren Sutcliffe
The Red Forge Publishing House with Kesbooks