Hair Growth Calculator

Adjust the calculator values below

Projected final hair length 16 in
Estimated time to target Not used — projection mode
Net retained length change 6 in
Biological growth before retention 6 in
Retained biological growth 6 in
Estimated trimming or removal 0 in
Effective net growth rate 0.5 in/month
Duration in months 12 months
Equivalent duration in days 365.243 days
Current hair length 10 in
Target hair length Not used — projection mode
Calculation status Projection from the selected average assumptions
16 in
Projected final hair length 10 in current length + 12 months at 0.5 in/month
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Hair Growth Calculator

Project future hair length or estimate time to a target using current length, growth rate, retention, trims, and mixed metric or imperial units.

Use an average growth rate as a planning assumption

The source calculator uses an average scalp-hair growth rate of 0.5 inch per month. This calculator lets you change that rate and its unit because individual growth varies and a measured personal rate can be more useful than the default.

Choose a projection or a target-time calculation

Projection mode adds effective retained growth over the selected duration to current length. Target mode divides the additional length needed by the effective net growth rate. Explicit modes avoid treating current length, final length, growth amount, and time as simultaneously independent inputs.

Separate biological growth from retained length

Biological growth is the selected monthly rate multiplied by time. The retention percentage models how much of that new length remains after breakage or shedding, and the trimming rate subtracts average length removed per month. These are planning assumptions rather than measurements of follicle activity.

Treat the result as an estimate, not a medical prediction

Hair grows in cycles, and visible length change can differ with genetics, age, health, hormones, nutrition, hair type, care practices, breakage, shedding, trims, and measurement method. Sudden or concerning hair loss or scalp changes need appropriate medical evaluation rather than a length projection.

Frequently asked questions

Common questions about average hair growth, future-length projections, target timing, length retention, trims, mixed units, and individual variation.

What is the average hair growth rate?

The default planning rate is 0.5 inch per month, or 1.27 centimeters per month. It is an average rather than a prediction for one person, so use a measured personal rate when available.

How is projected future hair length calculated?

Convert the duration to months, multiply it by the biological growth rate and retention percentage, subtract average trimming or removal, and add the resulting net length change to current hair length.

How is the time to a target length calculated?

Subtract current length from target length, then divide by the effective net monthly growth rate. If the target is already met, the time is zero; if trimming exceeds retained growth, a longer target cannot be reached under those assumptions.

What does length retention mean?

Length retention is the share of biological growth that remains as visible length after modeled breakage or shedding. It does not change the follicle's biological growth rate; it changes the amount of length retained.

How should I enter occasional trims?

Convert them to an average monthly rate. For example, trimming 1 inch every 4 months is an average removal rate of 0.25 inch per month.

Why might my actual hair length differ from the estimate?

Hair grows in cycles and varies with genetics, age, health, hormones, nutrition, hair type, care, breakage, shedding, trims, and measurement technique. Concerning hair loss or scalp changes need appropriate medical evaluation.