Amaŋmaŋ tuma. Basic geometry is from the description of the large 130cm × 195cm flag, and the specification drawing found in Rwanda Law N° 34/2008.

Article 2: The national flag shall be made up of three (3) colours: green, yellow and blue. The flag shall comprise of the following colours from the bottom to the top: a green strip, followed by a yellow strip both of which cover half the flag. The upper half is blue and bears on its right hand side the image of the sun with its rays of golden yellow. The sun and its rays are separated by a blue ring.

...

Article 4: 1° A large flag shall be meant to be displayed before administrative buildings and where ever it is required. This flag shall be one hundred and ninety-five centimetres (195 cm) long and one hundred and thirty centimetres (130cm) wide and shall not have strands. ... The pieces of cloth in green and yellow colours shall be both sixty-five (65 cm) centimetres wide; each piece is thirty-two centimetres and half (32.5 cm) wide.

The piece of cloth in blue colour shall be sixtyfive centimetres (65 cm) wide. The diameter of the sun shall be thirteen centimetres (13 cm) and forty-two centimetres (42 cm) of its rays. The space between rays of the sun and the upper edge shall be thirteen centimetres (13 cm) while the space between rays and the right hand side edge is fourteen centimetres (14 cm).

—  selected extracts from Law N° 34/2008 — Chapter 2

The legal text goes on to list dimensions for three other sizes: 30cm × 20cm, 225cm ×150cm, & 210mm × 140mm. Due to intentional rounding, the dimensions pertaining to the sun are not perfectly scaled between the different sizes.

The legal text does not provide any dimensions for the blue ring. If the blue ring truly separates the sun from its rays (as explictly stated in the text), then one could assume that the yellow circle inside the ring is to be treated for legal purposes as "the sun"; the diameter of the sun is given as 13cm which implies the inner diameter of the blue ring could be 13cm. Alternatively one may assume that the diameter of the "sun" is equivalent to the diameter of an imaginary circle running through the sun's inner vertices.

A black and white flag specification drawing can be found in an annex for Law N° 34/2008; it is on page 42 of the document referenced above. Fractional dimensions are given on the page 43. There drawing is poor quality:

• The sun is much closer to both the top and right edges of the flag than dictated by the text in chapter 2.
• The diameter of the sun's rays is about 14% larger than dictated by the text in chapter 2.
• The sun is rotated about 2° clockwise for no apparent reason.
• The diamter of the sun's rays (labeled as D) is listed on page 43 as being 0.125Y where Y length of the flag; this is wrong; it should be D=¹⁴⁄₆₅Y ≈ 0.21538461Y.

Observations:

• There are two circles on the specification sheet which are assumed to be the outer and inner edges of the blue ring.
• The outer circle appears to pass through all the inner vertices of the sun's rays. It is given a dimension of 0.1 times the width of the flag which matches the diameter of the "sun" documented in the text on page 27.
• The inner circle has no label and no specified diameter.
• A third circle would have hypothetically indicated a gap between the inner star vertices and the ring, but no third circle exists on the drawing.

For the purposes of this Wikimedia construction sheet:

• The sun's outer vertices are placed in an imaginary circle with a diameter equal to 42 units which is the value specified for the sun's rays in chapter 2.
• The sun's inner vertices are placed in an imaginary circle with a diameter equal to 13 units which is the value specified for the "sun" in chapter 2.
• The outer edge of the blue ring is a circle drawn through the inner vertices of the Sun as shown on the specification drawing.
• The ring is given a thickness of ~0.75 units because that is the approximate width of the gap between the two circles in the specification drawing. The resulting inner diameter of the ring is approximately 11.5 units and is labeled as such.

The government maintains representations of the flag in EPS and JPG formats at www.gov.rw/documents/national-symbols. The website says "The characteristics, description, ceremonial and respect of the National Symbols are determined by the law." However, the EPS and JPG drawings are drastically different than anything documented in Law LAW N° 34/2008. The discrepancies include:

• The flags are stretched horizontally which results in a non 2:3 ratio and an elliptical sun.
• The widths of the green and yellow bars are not equal.
• The combined width of green and yellow bars does not equal the width of the blue bar.
• The Sun is rotated by 7.5°.
• The diameter of an imaginary circle through the sun's inner vertices is about 61% larger than specified by the law; this creates a large gap between the blue ring and inner vertices.
• The sun is much closer to both the top and right edges of the flag than dictated by the text in chapter 2 of the law.

Most photographs of flags used by the government have a gap between the blue ring and the inner vertices of the sun. Olympic flag manuals published by the IOC between 2012 and 2020 show a similar gap.