The notes of the flute are determined chiefly by the size and placement of the fingerholes.
The chart below gives a rough guide to where to put the holes. The chart’s measurements are shown as percentages of distance from the mouthhole. All measurements are from hole centers, not edges.
The chart provides a starting point only. From there, you will have to experiment with final placement and hole size, using tuning techniques such as the ones we’ll now discuss. (For more advanced techniques, see my book, Simple Flutes.)
Here are the two most important rules for tuning:
A hole will give a higher note if it is placed closer to the mouthhole. It will give a lower note if placed farther away.
A hole will give a higher note if made larger. It will give a lower note if smaller.
These rules mean you can “raise” a note by enlarging the hole or by placing the hole closer to the mouthhole. You can “lower” the note by using a smaller hole or by placing the hole farther from the mouthhole.
It also means you can change the hole size and its placement without changing the note. A larger hole could be placed farther from the mouthhole, or a smaller hole placed closer to the mouthhole.
For tuning, the notes of the flute can be compared to the notes of a piano, pitchpipe, or other tuning instrument. Or you can simply tune the notes of the flute to each other, in the do-re-mi pattern, with the low note as do.