Clay flute hole finder

Measure the tube you made, or pick a key and a scale, and this page tells you where to put the mouth hole and the finger holes. Everything runs on your phone; nothing is sent anywhere.

Your tube

Key (the lowest note, all holes covered)

Scale Pentatonic scales need only four finger holes.

Inside length

From the open end to the stopper (the inside of the closed end). Slide a thin stick inside, mark it at the open end, and measure the stick.

Inside diameter

The width of the hole inside the tube.

Clay shrinkage

How much the clay shrinks from now until it comes out of the kiln. Not sure? Keep 12% and see how to measure it.

Wall thickness

Thicker walls need bigger holes. Leave empty to use 1/8″ (3 mm), the middle of the book's range.

More options

Finger hole size after firing

The book suggests 3/8″ to 7/16″. Smaller holes sit closer together and are easier to reach.

Mouth hole already made?

Distance from the center of the mouth hole to the open end. Leave empty to place the mouth hole the book's way.

Mouth hole size after firing

The book suggests 7/16″ or slightly larger.

Where to put the holes

Measure from

Hole	From open end	Drill now

After firing

How to play the scale

Filled circles are covered holes. Hole 1, nearest the mouth hole, is on the left. A note sounds when its hole is the highest one open: cover the holes between it and the mouth hole, and leave it and the holes past it open.

Tap a note to hear it in tune, then match it on the flute. On an iPhone, turn off silent mode to hear it.

Planning the next flute

The key of a flute is its lowest note, with every hole covered. To end up with a flute in a given key after firing, start with a tube about this long. It uses your wall thickness, shrinkage and inside diameter (or the book's diameter when you leave it empty).

Key	Inside length now	Inside diameter now

Tips from the book

No sound at all? Check the mouth hole first: its distance to the stopper, a clean sharp edge on the far side, and a wall that isn't too thick. The finger holes don't matter until the flute sounds with all of them closed.
The positions are a starting point. Drill a little small: you can always make a hole bigger, never smaller.
A hole plays higher when it's bigger or closer to the mouth hole, and lower when it's smaller or farther away.
The holes don't have to sit in a straight line. Shift them sideways if that makes them easier to reach.
Glaze can shrink the holes. Keep it out of them, or skip glazing.

Measuring your clay's shrinkage

Roll a flat bar of the same clay, at the same wetness as when you drill. Scratch two lines exactly 10 cm (or 4″) apart. Fire it with your flutes, then measure again. If the lines end up 8.8 cm apart, the shrinkage is 12%.