# Hair Growth Calculator

URL: https://speedycalculator.com/calculators/everyday-life/hair-growth/
Last updated: 2026-10-25

> The hair growth calculator estimates how long your hair will be after a number of months, and how long it will take to grow to a target length, at an average growth rate of about half an inch (1.25 cm) a month.

## Inputs

- Current length (in, cm)
- Target length (in, cm)
- Growth rate per month (in, cm, mm)
- Length lost to trims (%)
- Months to project

## Results

- Months to reach target
- Date estimate (from today)
- Length after the projected months
- Net growth per year

## Formula

```
Length gained = growth rate × months (≈ 0.5 in or 1.25 cm per month)
Months needed = (target length − current length) ÷ (growth rate × (1 − trim loss))
```

## Explanation

Scalp hair grows about 1–1.5 cm a month on average – roughly 15 cm (6 in) a year – though genetics, age, health and nutrition all play a part. Regular trims remove split ends but also some length, so they slow how fast hair appears to grow.

### How to use the Hair Growth Calculator

- **Current length**
- **Target length**
- **Growth rate per month**
- **Length lost to trims**
- **Months to project**

Results update as you type, and every field accepts the units shown in its menu.

### How it works

Enter your current length, your target length, your growth rate (or keep the average) and how much length trims remove.

### Tips

- Use the amounts printed on the product (ml, sheets, applications) where available.
- Count everyone in the household who shares the product.
- Buy a little extra so you never run out unexpectedly.
- Small daily habits add up – check the yearly figures for the real impact.

### Common mistakes to avoid

- Forgetting that hot water costs energy as well as water.
- Underestimating how much sunscreen a full application needs.
- Comparing pack prices without checking the size of each pack.

### Inputs explained

FieldWhat to enterCurrent lengthUnits: in, cmTarget lengthUnits: in, cmGrowth rate per monthUnits: in, cm, mmLength lost to trimsIn %Months to projectA number

### What each result means

- **Months to reach target** = max([Target length] - [Current length], 0)÷([Growth rate per month]×(1 - [Length lost to trims]÷100))
- **Date estimate (from today)** = today() + [Months to reach target]×30.44
- **Length after the projected months** = [Current length] + [Growth rate per month]×(1 - [Length lost to trims]÷100)×[Months to project]
- **Net growth per year** = [Growth rate per month]×(1 - [Length lost to trims]÷100)×12

### Example values

How the main result changes when **Current length** changes and everything else stays at the example values above:

Current length (in)Months to reach target524.47.518.91013.312.57.8152.2200

## Worked example

Inputs — Current length: 10 in; Target length: 16 in; Growth rate per month: 0.5 in; Length lost to trims: 10 %; Months to project: 12.

Results — **Months to reach target = 13.3**; Date estimate (from today) = Sat, December 4, 2027; Length after the projected months = 15.4 in; Net growth per year = 5.4 in.

## FAQ

**How fast does hair grow?**
About half an inch (1.25 cm) a month, or 6 in (15 cm) a year on average.

**Do trims make hair grow faster?**
No – hair grows from the root; trims keep ends healthy so length isn't lost to breakage.

**How long does it take to grow hair to shoulder length?**
From a short bob, often 1–2 years.

**What formula does the Hair Growth Calculator use?**
Length gained = growth rate × months (≈ 0.5 in or 1.25 cm per month).


## Sources

- [American Academy of Dermatology – Hair facts](https://www.aad.org/)