How big to cut a slab for a 12 oz mug

Slab sizes for a 12 oz mug, by clay type

All for a straight-sided mug 3.25 in across the outside after firing, with 1/4 in walls and base, holding 12 US fl oz (355 mL) to the brim. Only the cut sizes change with the clay; the finished mug is the same.

In centimetres, for mid-fire stoneware: wall slab about 29.5 × 11.2 cm, base disc 9.4 cm, firing to a mug 8.3 cm wide and 9.9 cm tall.

Wider or narrower: other 12 oz mug sizes

The same 12 oz can be a tall, narrow mug or a short, wide one. Pick the shape you like; the height follows from the width.

Mid-fire stoneware (~12%), 1/4 in walls and base, 12 oz to the brim.

Leave room at the top

These sizes hold 12 oz filled to the very rim. Nobody fills a mug that far, so if you want 12 oz of coffee with room to carry it, add about 1/2 in to the height. For the 3.25 in mug that's about 4.4 in tall after firing, or a 5.00 in tall wall slab in mid-fire stoneware.

Glaze, a thicker base or a foot ring also take up a little room, so it's safer to aim slightly bigger than to come out short.

The handle

A comfortable handle on a mug this size is about 4.5 in long and 3/4 in wide after firing. Shrinkage applies here too: cut the strip about 5.11 × 0.85 in in mid-fire stoneware.

How to work it out yourself

If you want a size that isn't in the tables, here's the method behind them.

1. Work out the inside of the finished mug. Inside radius = half the outside width, minus the wall thickness. For 3.25 in and 1/4 in walls: 1.625 − 0.25 = 1.375 in.
2. Turn ounces into cubic inches. 1 US fl oz = 1.805 cubic inches, so 12 oz = 21.66 cubic inches.
3. Find the inside height. Inside height = volume ÷ (π × radius²) = 21.66 ÷ (3.14 × 1.375²) = 3.65 in.
4. Add the base. Outside height = 3.65 + 0.25 = 3.9 in.
5. Scale up for shrinkage. Divide every outside measurement by (1 − shrinkage): 3.9 ÷ 0.88 = 4.43 in tall; 3.25 ÷ 0.88 = 3.69 in for the base disc.
6. Get the wall length. π × the scaled-up width: 3.14 × 3.69 = 11.60 in.

Tapered mugs are trickier, because the inside is a cone slice rather than a cylinder and the wall template is a curved band instead of a rectangle. The guide to making pottery templates covers the curved shape, and how to calculate clay shrinkage explains the shrinkage step in detail.

How to do it in Slab Marks

The template maker works backwards from the capacity you want, so you don't need the method above at all. Hold a capacity, and whatever size you change, the others adjust to keep it.

1. On the homepage, pick Mug.
2. Type 12 in Target capacity. The mug resizes to hold 12 oz, keeping its shape, and the lock next to the field closes to show the capacity is being held. Click fl oz to switch to mL.
3. Set the bottom and top diameter to 3.25 in for straight sides. The height adjusts to 3.90 in so the mug still holds 12 oz. Change the height instead, and the diameters adjust.
4. Open Clay body and pick your clay. Open Handle to choose a handle style.
5. Click Print template, then Print directly, at 100% scale. The wall, base and handle are all on the pages.

Common questions

How many mL is a 12 oz mug?

12 US fluid ounces is about 355 mL. A 350 mL mug works out almost the same.

What about an 8 oz, 10 oz or 16 oz mug?

Use the same method with a different volume, or let the template maker do it: enter the capacity you want and it works out the height for you.

Do the sizes include extra for the seam?

No. The wall length is exactly the distance around the mug. Bevel the two ends so they meet in a long, angled join, then score and slip.