Alongside these traditional sizes, you will also find paper in A sizes, as well as a wide range of pads and blocks. So what do they all mean?

What is an ‘Imperial’ sheet?

The traditional full sheet of watercolour paper is known as an Imperial Sheet (or Full Imperial) and measures 560 × 760mm (22 x 30”).

The sheet can then be divided to create smaller sizes:

Imperial size        Approximate dimensions
Full Imperial          560 × 760mm / 22 × 30"
Half Imperial          380 × 560mm / 15 × 22"
Quarter Imperial    280 × 380mm / 11 × 15"

An Imperial sheet can be divided into two 'Half Imperial' sheets, or four 'Quarter Imperial' sheets.

This is one of the useful things about buying paper as a full sheet. You can use the whole sheet for a larger painting, or divide it down to suit what you are working on. Quarter Imperial, at 280 x 380mm, is a particularly familiar watercolour format. It is large enough to develop a painting, while still being easy to handle.

Why do watercolour artists still use Imperial sizes?

The Imperial sheet size may seem unusual now that most paper is sold in A sizes, but they remain part of the language of watercolour. ’Imperial’ is a historic sheet name and comes from a time when paper sizes had wonderful names such as Elephant, Royal and Foolscap.

The traditional sheet size has been used by artists and paper makers for generations, with Half and Quarter Imperial developing naturally from the full sheet. The names have simply stayed with us.

There is also something about the proportions. An Imperial sheet is a little wider than many of the paper sizes we use every day. It gives a composition room to breathe without feeling stretched, which works particularly well for watercolour.

What does the order of the dimensions mean?

You may see a sheet described as 560 x 760mm in one place and 760 x 560mm somewhere else.

With paper, the order of the dimensions can indicate the grain direction, with the second dimension being the direction in which most fibres lie. This can be useful when folding, as it creates a neater edge. For example, Saunders Waterford® is 560x760mm whilst Bockingford® is 760x560mm, which indicates different grain directions. The grain in Mould Made paper is less pronounced than in machine-made papers, but it is still worth being aware of.

Inches or metric measurements

Historically, papermills would have made paper in inches. This has been superseded by metric measurements. So a 22 x 30” sheet is actually made to the metric 560 x 760mm size, and given the nominal imperial inch equivalent. In the UK (and US) many artists still refer to paper sizes using the imperial inch name, just because it is a bit more catchy and memorable to say.

How do A sizes compare?

The A series is the international standard, tied to the metric paper system, that most people are familiar with. A4 is the standard sheet used for everyday printing, with A3, A2 and A1 becoming progressively larger. One useful feature of the A series is that when a sheet is cut in half, the proportions remain the same.

The A sizes most commonly encountered in watercolour are:

A size Dimensions
A1 594 × 841mm     Similar to Full Imperial 560 x 760mm
A2 420 × 594mm     Similar to Half Imperial 380 × 560mm
A3 297 × 420mm     Similar to Quarter Imperial 280 × 380mm
A4 210 × 297mm
A5 148 × 210mm

For example, an A3 sheet is slightly larger than a Quarter Imperial sheet. If you need your paper to fit a particular mount or frame, it is always worth checking the actual dimensions.

What about watercolour pads?

Pads are a convenient way to buy watercolour paper, particularly for sketching, travelling or everyday painting.

You will find pads and blocks in traditional sizes including 260 x 180mm (10 x 7”), 310x230mm (12 x 9”), 360 x 260mm (14 x 10”), 410x 310mm (13 x 12”), plus A sizes, from smaller A5 and A4 formats through to larger A3 pads. The traditional pad sizes follow framing sizes, and have evolved as they are pleasing shapes to the eye when displaying artwork.

Choosing your size

Which size you choose will depend on what you are painting and how you like to work. A smaller sheet can be useful for sketches and studies, while Quarter Imperial gives you more space to develop a subject. Half Imperial and Full Imperial allow you to work on a larger scale.
At St Cuthberts Mill, we continue to make our watercolour papers in traditional sheet sizes alongside a range of convenient pad and block formats, giving artists a choice to suit the way they work.

Further reading
How to Choose the Right Watercolour Paper
Can I Paint on Both Sides?

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