free calculator
Hair Donation Length Calculator
How long does hair have to be to donate? Enter your length and what you want to keep to see how many inches you can cut and which common minimums you meet.
How to use the Hair Donation Length Calculator
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Measure your hair pulled straight
Measure from your crown to the ends at the back and enter the number in inches or centimeters. Stretch curls and coils until they are straight.
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Enter the length you want to keep
Type how long your hair should be after the cut. The calculator subtracts it from your current length.
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Add your shortest layer if your hair is layered
Tick the layers box and enter the shortest layer, because many programs measure the shortest hair in the ponytail.
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Press “Check my donation length”
You see the most you can donate, the length level you keep, and whether you meet minimums of 8, 10, 12 and 14 inches.
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Check your organization’s rules
Requirements differ between programs, so read the current guidelines of the one you choose before you book the cut.
How the hair donation length is worked out
A hair donation is a ponytail or a set of braids cut off in one piece. Whether you can donate comes down to one subtraction: the length you have today, minus the length you want to keep on your head.
most you can donate = current length − length you keep
months to a minimum = (length you keep + minimum − current length) ÷ growth per monthMeasure pulled straight
Enter your length from the crown to the ends at the back, with the hair pulled straight. Curly and coily hair is measured stretched, because programs measure the ponytail straight. If you only know how long your hair looks when it is dry, the hair shrinkage calculator shows how much length the curl is hiding.
Layers
In a layered cut the hairs in the ponytail are not all the same length. Some programs measure the longest layer and others the shortest, so the calculator works out both. The table uses the shortest layer, and marks a row “longest layer only” when just your longest hair reaches that minimum.
Common minimums, not one organization’s rule
The table checks ponytail lengths of 8, 10, 12 and 14 inches because those are the minimums donors most often come across. They are examples. Each program sets its own minimum and its own rules on layers, gray hair, and color-treated, relaxed or other chemically treated hair, and those rules change. Always read the current guidelines of the organization you choose before you book the cut.
Months of growth
For every minimum you miss, the calculator divides the missing inches by your growth per month and rounds up to whole months. The default of 0.5 inch a month is a rule of thumb. Measured growth varies a lot from person to person, and one study recorded an average close to 0.3 inch a month for Afro-textured hair, so lower the rate if your hair grows slowly. The estimate assumes no trims and no breakage.
What the calculator cannot tell you
It cannot tell you whether a program will accept your hair, and it does not know how your stylist will shape what is left. The length level in the result comes from the hair length chart for a woman of average height, so it can be one level off on a shorter or taller body.
Hair length needed to donate, by the length you keep
| Length you keep | To donate 8 in | To donate 10 in | To donate 12 in | To donate 14 in |
|---|---|---|---|---|
| Chin length — 9 in | 17 in (43 cm) | 19 in (48 cm) | 21 in (53 cm) | 23 in (58 cm) |
| Shoulder length — 12 in | 20 in (51 cm) | 22 in (56 cm) | 24 in (61 cm) | 26 in (66 cm) |
| Armpit length — 15 in | 23 in (58 cm) | 25 in (64 cm) | 27 in (69 cm) | 29 in (74 cm) |
| Bra-strap length — 18 in | 26 in (66 cm) | 28 in (71 cm) | 30 in (76 cm) | 32 in (81 cm) |
Total stretched length you need today, crown to ends. Length levels are for a height of 5 ft 4 in; minimums are common examples, not the rule of any one organization.
Time to grow the missing length
| Length still needed | At 0.5 in a month |
|---|---|
| 1 in (3 cm) | about 2 months |
| 2 in (5 cm) | about 4 months |
| 4 in (10 cm) | about 8 months |
| 6 in (15 cm) | about 1 year |
Estimates with no trims or breakage.
Frequently asked questions
How long does hair have to be to donate?
How do I measure my hair for donation?
Can I donate layered hair?
Can I donate color-treated, relaxed or bleached hair?
How long will it take to grow my hair long enough to donate?
How short will my hair be after I donate?
Does curly or coily hair need to be longer to donate?
Sources
Last data update:
- Loussouarn G. African hair growth parameters. Br J Dermatol. 2001;145(2):294-297. Afro-textured hair grew about 256 µm/day in the study sample — slower than Asian and Caucasian samples.
- Loussouarn G, Lozano I, Panhard S, et al. Diversity in human hair growth, diameter, colour and shape. An in vivo study on young adults from 24 different ethnic groups observed in the five continents. Eur J Dermatol. 2016;26(2):144-154. Growth rate, diameter and curl shape vary widely between and within groups.
How we research and update pages: editorial policy. Spotted an error? Tell us.
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