Oblong-Face Brow Chart

The five lines to measure, the tail-drop sweep from level to 30 degrees at three tail runs, what a trim of five or ten millimetres is worth as a share of the brow, the inner-gap and lid-gap arithmetic, and a test log ordered by what each step costs to undo. Print it or keep it on your phone.

1. The five lines to measure

1. Brow lengthInner start to the tip of the tail, following the brow rather than cutting across it. mm = in
2. Tail runHorizontal distance from the highest point of the brow to the tip of the tail. Every drop figure in section 2 depends on this one, so take it even if nothing else on this sheet asks you to. mm = in
3. Tail dropHow far the tip falls below the level of the inner start. Negative if it finishes higher. mm = in
4. Inner gapBetween the two inner ends, across the bridge of the nose. mm = in
5. Lid gapUpper lash line to the underside of the brow, taken where that distance is narrowest. mm = in
Face lengthHairline midpoint to chin. Used only in section 5, to turn a raise into a share of the face. mm = in
Front edge below the hairlineHairline midpoint down to the inner start of the brow. Also used only in section 5. mm = in

Every inch figure on this sheet is the millimetre figure divided by 25.4. That division is exact arithmetic rather than a rounded approximation, because the inch has been defined as exactly 25.4 mm since 1959. Worked: 9.10 ÷ 25.4 = 0.35827, printed here as 0.36 in. A flexible tape works; so does a strip of paper you mark and then lay against a ruler.

2. Tail-drop sweep, level to 30 degrees

How far the tip of the tail sits below the level of the inner start, at three tail runs. Drop = tail run × tan(tilt). Each cell gives millimetres and inches.
Tilt below level	20 mm run	25 mm run	30 mm run
0° (level)	0.00 mm / 0.00 in	0.00 mm / 0.00 in	0.00 mm / 0.00 in
5°	1.75 mm / 0.07 in	2.19 mm / 0.09 in	2.62 mm / 0.10 in
10°	3.53 mm / 0.14 in	4.41 mm / 0.17 in	5.29 mm / 0.21 in
15°	5.36 mm / 0.21 in	6.70 mm / 0.26 in	8.04 mm / 0.32 in
20°	7.28 mm / 0.29 in	9.10 mm / 0.36 in	10.92 mm / 0.43 in
25°	9.33 mm / 0.37 in	11.66 mm / 0.46 in	13.99 mm / 0.55 in
30°	11.55 mm / 0.45 in	14.43 mm / 0.57 in	17.32 mm / 0.68 in

The 20 mm, 25 mm and 30 mm runs are stand-ins, not targets. Read down the column nearest your own tail run, or interpolate. Two things the table shows that the adjectives do not: five degrees of tilt is a tenth of an inch or less at every run here, so a tail described as dropping "a little" and a tail described as level are the same object on a tape; and the run matters as much as the angle, since thirty degrees on a 20 mm run and twenty degrees on a 30 mm run differ by less than a millimetre of drop even though the tilts differ by ten degrees.

For comparison: how far the tip travels if the tail's direction is rotated by 30 degrees instead of tilted down by 30 degrees. Travel = 2 × run × sin(15°).
Tail run	Tip travels	In inches	Against the sweep above
20 mm	10.35 mm	0.41 in	more than the whole distance from level to 25° down on the same run
25 mm	12.94 mm	0.51 in	more than the whole distance from level to 25° down on the same run
30 mm	15.53 mm	0.61 in	more than the whole distance from level to 25° down on the same run

A rotation and a tilt are different instructions and they are routinely written as the same one. Rotating the tail's direction by 30 degrees moves the tip along an arc, and the chord of that arc is 2 × run × sin(15°); tilting it down by 30 degrees moves the tip straight down by run × tan(30°). The rotation is the smaller of the two at every run in these tables — 12.94 mm against 14.43 mm at a 25 mm run — so a brow set by one is not a brow set by the other. One approximation is being made and it is worth naming: the run is used above as the radius of the rotation, and the tail is a curve, so its length along the brow is longer than its horizontal run and the true travel is larger than the figure printed.

3. What "a bit" and "too long" are worth

The same two cuts, expressed as a share of four different brow lengths. Share = cut ÷ brow length.
Brow length	In inches	5 mm off is	10 mm off is	The cuts themselves
50 mm	1.97 in	10.0% of the brow	20.0%	0.197 in / 0.394 in
55 mm	2.17 in	9.1% of the brow	18.2%	0.197 in / 0.394 in
60 mm	2.36 in	8.3% of the brow	16.7%	0.197 in / 0.394 in
65 mm	2.56 in	7.7% of the brow	15.4%	0.197 in / 0.394 in

Read the last column against the first two. The instruction is the same length of hair in every row and it is not the same change: five millimetres is a tenth of a 50 mm brow and a thirteenth of a 65 mm brow. Any advice that specifies the cut without specifying the brow it is cut from is giving you a number dressed as a judgement.

4. Inner-gap arithmetic

What drawing the inner ends closer does to the gap between them. Each figure is millimetres and inches, with the share of the original gap it removes. New gap = original − (2 × millimetres per side).
Inner gap now	1 mm per side	2 mm per side	3 mm per side
16 mm / 0.63 in	14 mm / 0.55 in, −12.5%	12 mm / 0.47 in, −25.0%	10 mm / 0.39 in, −37.5%
18 mm / 0.71 in	16 mm / 0.63 in, −11.1%	14 mm / 0.55 in, −22.2%	12 mm / 0.47 in, −33.3%
20 mm / 0.79 in	18 mm / 0.71 in, −10.0%	16 mm / 0.63 in, −20.0%	14 mm / 0.55 in, −30.0%
22 mm / 0.87 in	20 mm / 0.79 in, −9.1%	18 mm / 0.71 in, −18.2%	16 mm / 0.63 in, −27.3%

This is the only edit on the sheet that changes the brow's proportions by addition rather than removal, which is why it is the one worth trying first. Two millimetres of drawn hair per side takes a fifth off a 20 mm gap and nothing off your brow. The starting gaps in the first column are stand-ins; substitute your own measurement from section 1.

5. Lid-gap and raise arithmetic

What raising the front edge of the brow does to the space over the lid. New lid gap = original + raise.
Lid gap now	Raise 1 mm	Raise 2 mm	Raise 3 mm
8 mm / 0.31 in	9 mm / 0.35 in	10 mm / 0.39 in	11 mm / 0.43 in
10 mm / 0.39 in	11 mm / 0.43 in	12 mm / 0.47 in	13 mm / 0.51 in
12 mm / 0.47 in	13 mm / 0.51 in	14 mm / 0.55 in	15 mm / 0.59 in

The same raise expressed against the whole face, using a 190 mm face length and a front edge sitting 60 mm below the hairline. Both are stand-ins.
Raise	Share of face length	Front edge moves from 31.6% of face length to
1 mm	0.53%	31.1%
2 mm	1.05%	30.5%
3 mm	1.58%	30.0%

Share = raise ÷ face length, so 2 ÷ 190 = 1.05%. Position = (front edge below hairline − raise) ÷ face length, so (60 − 2) ÷ 190 = 30.5%. Replace 190 with the face length you took in section 1 and 60 with your own front-edge figure, then redo both divisions. The two-millimetre raise is visible on a brow and is barely one percent of a face, and those are the same fact stated twice; which of them the instruction meant is never specified.

6. Test log, ordered by what each step costs to undo

Work down the list, not across it. Wear each change long enough to see it in daylight and in a photograph before you decide about the next one, and change only one row at a time.
Step, cheapest to undo first	What it costs to undo	Date started	Verdict
Brush the hairs up and out, hold with a clear gel	One wash
Set them upright with soap and a spoolie instead	One wash
Draw individual hairs into the inner ends	One wash; removes nothing
Change the tail's direction by setting it, not cutting it	One wash
Trim the tail	Weeks to months of growth, and no length was ever specified for the cut
Pluck a few hairs from under the front to raise it	Months; there is a warning on record that hair plucked long enough may not return as it did
Pigment, hair stroke by hair stroke	The longest item here. Published durations disagree with each other, so no figure is printed on this sheet
A growth serum	Stopping it. Read the actives before buying: the class this caution is about is documented to cause fat loss around the eye when used as a drop, and whether a brow serum carries the same risk is not established

Before row five, measure the tail drop and compare it with section 2. If your drop is inside the distance between level and twenty degrees at your own tail run, the instruction you are about to follow was not written about your face.
Before row six, measure the inner gap and work through section 4. Drawing two millimetres per side narrows a 20 mm gap by a fifth and takes no hair out; raising the front by the same two millimetres does.
Treat any step that happens in a professional chair as a separate category from the rest of this log. Repeated reshaping is one of the ways a tail thins in the first place, and a shape chosen there is chosen against the chair's reference images rather than against your measurements.