Hair Extension Calculator
Work out how many grams, packs or bundles of hair extensions you need. A full head is usually about 100–200 g — this calculator adjusts that for your length, hair density, the fullness you want and your method, then converts it into packs, wefts or bundles.
How many grams of hair extensions do you need? How many bundles for a sew-in, or packs of tape-ins? Enter your current and target length, choose your hair density, fullness and extension method, and this hair extension calculator estimates the grams to buy and the number of packs or bundles that means.
Enter your lengths, pick your hair type and method, then press Calculate.
Hair extension cost calculator
Estimate what your extensions will cost: packs × price per pack + salon install fee. Use the number of packs or bundles from the How many do I need? tab.
Enter your packs, price and install fee, then press Calculate.
How the hair extension calculator works
Extensions are sold and installed by weight in grams, so the real question behind “how many packs” or “how many bundles” is always how many grams you need. This calculator starts from a typical full‑head baseline of about 150 grams and adjusts it three ways: your natural density (thicker hair needs more hair to blend into), the fullness you want, and your target length — because the same weight of hair looks thinner the longer it is stretched. It then converts those grams into the unit your method actually comes in, whether that is clip‑in sets, tape‑in packs, keratin strands, hand‑tied wefts, or weave bundles.
Because grams are the shared measurement across every method, you can compare them fairly: 150 grams is roughly 3 tape‑in packs, about 60 tape pieces, or 2 sew‑in bundles. Treat the number as a well‑reasoned starting point — a stylist fine‑tunes it for your face shape, layering and texture.
The hair extension formula
- 150 — typical full‑head baseline in grams
- Density — fine 0.75, medium 1.0, thick 1.35
- Fullness — subtle 0.7 up to extra‑full 1.6
- Length — steps up from 0.8 (short) to 1.7 (30 in+)
How many grams of hair extensions do you need?
| Your hair & look | Full‑head guide |
|---|---|
| Fine hair, subtle length/volume | 80 – 120 g |
| Medium hair, everyday full head | 120 – 160 g |
| Thick hair, or long (20–24 in+) | 160 – 220 g |
| Extra length (26–30 in+) | 200 – 250 g |
| Sew-in / weave (≈100 g per bundle) | 2 – 4 bundles |
These ranges are drawn from the guidance published by hair‑extension brands and stylists. The right number for you sits inside the range, which is exactly what the calculator estimates from your own inputs.
Packs, wefts and bundles by method
The grams stay similar; only the packaging changes. Clip-ins come as full sets of about 100–120 g. Tape-ins come in packs of roughly 20 pieces (about 40–50 g), with each tape piece near 2.5 g. Keratin / K-tip bonds are sold in packs of strands. Micro-link (micro-bead / i-tip) extensions are also strand-by-strand, attached with small beads at about 1 g per strand. Hand-tied wefts are bought individually at about 20 g each. Sew-in / weave hair comes in bundles of about 100 g, and most full heads use 2 to 4 bundles. Choosing the right method matters as much as the weight: a lighter method protects fine hair, while thick or long hair blends best with more grams spread over more pieces.
Where will your extensions fall?
Length is measured in a straight line, so the same number of inches lands in a different spot on everyone. As a rough guide measured down the back, 14 in reaches the shoulders, 18 in the upper back, 20–22 in the mid-back, 24 in around the waist, and 26 in and beyond toward the hips. Taller frames carry the same length a little higher, which is why the calculator lets you set your height to estimate where your chosen length will fall. Curly and wavy textures also look 1–2 inches shorter in the pack than when stretched, so allow for that shrinkage.
Hair extension length chart (inches to where it falls)
| Length | Where it falls* | Typical full head |
|---|---|---|
| 12 in | Chin to collarbone | 90–120 g |
| 14 in | Shoulders | 100–140 g |
| 16 in | Below shoulders | 110–150 g |
| 18 in | Armpit / upper back | 120–160 g |
| 20 in | Mid-back | 150–190 g |
| 22 in | Below mid-back | 160–200 g |
| 24 in | Waist | 180–220 g |
| 26 in | Upper hip | 200–240 g |
| 28 in | Hips | 220–260 g |
| 30 in | Below hips | 240–280 g |
*Measured straight down the back on an average height of about 5'4" to 5'6". Taller frames carry each length a little higher, and curly or wavy textures look 1–2 inches shorter in the pack. Set your height in the calculator above for a personalised estimate of where your length will fall.
Estimate only — a starting point, not a prescription. The exact amount also depends on your face shape, layering, hair texture and finished look. Confirm with your stylist or the extension brand before you order, especially for a first install.
How to use it & key terms
Enter your current length and target length in inches, pick your natural density and the fullness you want, choose a method, then press Calculate to see the grams needed and how many packs, wefts or bundles that is.
| Term | What it means |
|---|---|
| Current length | How long your natural hair is now, in inches. |
| Target length | The final length you want with extensions in. |
| Natural density | How thick your own hair is; thicker needs more grams to blend. |
| Fullness | How dramatic the result is, from subtle to extra full. |
| Grams | The weight of extension hair — the number brands sell by. |
| Pack / weft / bundle | The unit a method comes in, converted from grams. |
Sources & methodology
The calculator starts from a full‑head baseline of about 150 grams and multiplies it by a density factor (0.75 for fine hair up to 1.35 for thick), a fullness factor (0.7 for subtle up to 1.6 for extra full), and a length factor that steps up in brackets as the target length grows (0.8 at 14 inches or under, 1.0 to 18 inches, 1.2 to 22 inches, 1.45 to 26 inches, and 1.7 beyond). The gram figure is shown as a range of about plus or minus 15 percent to reflect that stylists treat weight as a starting point. Grams are then divided by the typical unit weight of the chosen method — roughly 110 g per clip‑in set, 50 g per tape‑in pack (2.5 g per piece), 40 g per keratin pack, 50 g per micro‑link pack (about 1 g per strand), 20 g per hand‑tied weft, and 100 g per weave bundle — and rounded up to whole units.
Sources: Published hair‑extension weight and quantity guides from extension brands and professional stylists (full‑head totals of about 100–200 g; ~100 g per weave bundle; ~2.5 g per tape piece). Figures are industry rules of thumb and should be confirmed with your stylist or supplier.
Choosing a method for your hair type — and caring for it
The grams and packs this tool estimates answer how much hair to buy, but choosing the right method for your own hair is what makes extensions look natural and stay comfortable. Fine or thin hair generally does best with lighter, gentler methods that spread their weight over a wide area, because heavy attachments on delicate strands can tug and become visible. Thick hair can carry more grams and more robust methods without looking sparse, though it needs enough hair added to blend so the extensions do not sit as an obvious separate layer. Very short hair limits which methods can hide their attachment points, and hair that has been coloured, relaxed or heat-damaged may need a gentler approach — and an honest look from a stylist — before anything is added at all.
It also helps to think in terms of commitment and upkeep. Clip-in styles go in and out in minutes and suit occasional wear or a single event, while tape-ins, keratin bonds, micro-links and hand-tied wefts stay in for weeks at a time and become part of your daily routine. Longer-wear methods usually look the most seamless, but they ask for more care and regular salon visits in return. The hair itself lasts noticeably longer when it is genuine human hair that can be washed, gently heat-styled and, with the semi-permanent methods, moved up and reused as your own hair grows. How long a set truly lasts depends far more on how it is treated week to week than on the day it was first fitted.
Maintenance is where that longevity is won or lost. Semi-permanent extensions need periodic move-up appointments as your natural hair grows and the attachment point drifts away from the scalp, and skipping them lets bonds tangle or pull. A few simple habits protect both the extensions and the hair underneath them:
- Brush gently from the ends upward, holding the roots to take the strain off the attachments.
- Keep heat moderate and use a heat protectant, since extension hair cannot repair itself the way living hair does.
- Tie hair loosely before sleeping or exercise so it does not tangle or drag at the roots.
- Follow your stylist's washing and product advice, and give your own hair a break between long-term sets.
Frequently asked questions
How many grams of hair extensions do I need for a full head?
A full head of extensions usually takes about 100 to 200 grams of hair, with roughly 150 grams being the most common choice. Fine hair adding subtle length needs less (around 80 to 120 grams), while thick hair or long lengths of 20 inches and beyond need more (about 160 to 220 grams). Enter your own length, density and method above for a tailored estimate.
Is 100 grams of hair enough for a full head?
For fine hair, or for adding moderate length and volume, 100 grams is often enough for a full head. If your natural hair is thick, or you want dramatic length or fullness, you will usually need 150 to 220 grams so the extensions blend without looking sparse. This calculator adjusts the gram estimate for your hair density and the look you want.
How many bundles of hair do I need for a sew-in or weave?
Most full-head sew-ins use 2 to 4 bundles, since a standard bundle holds about 100 grams of hair. Shorter lengths under 18 inches often need 2 to 3 bundles, while longer 22 to 30 inch installs usually need 3 to 4 because the same weight is stretched over more length and looks thinner. Add one bundle for extra fullness or a large head size.
How many packs of tape-in extensions do I need?
Tape-in packs usually hold about 20 pieces and roughly 40 to 50 grams. Adding volume only takes about 2 packs (40 pieces), a full head is typically 3 to 4 packs (60 to 80 pieces), and long or thick hair can need 4 to 6 packs. Each tape piece weighs about 2.5 grams, so the calculator converts your gram estimate into pieces and packs for you.
How many grams of hair extensions do I need for thin or fine hair?
Fine or thin hair generally needs fewer grams to blend, often 80 to 120 grams for a full head, because there is less natural density to match. The trick with fine hair is choosing a lighter method such as thin tape-ins or clip-ins so the weight does not stress the roots. Pick Fine density above and the calculator lowers the gram estimate accordingly.
How many grams do I need for long hair, like 20, 24 or 30 inches?
Longer hair needs more grams to keep density from root to tip, because the same weight looks thinner the longer it is stretched. As a guide, 18 to 22 inch lengths often use 100 to 150 grams, 24 to 28 inches use 150 to 200 grams, and 30 inches or more can need 200 to 250 grams. The calculator raises the estimate in brackets as your target length increases.
Does the amount depend on the extension method?
The total grams of hair are similar across methods, but how they are packaged differs. Clip-ins come in full sets, tape-ins in packs of about 20 pieces, keratin or K-tip bonds in packs of strands, hand-tied hair in individual wefts, and weave hair in bundles of about 100 grams. This calculator gives the grams and then converts them into the right unit for the method you choose.
How accurate is this hair extension calculator?
It gives a reliable starting estimate based on hair-industry gram guides, but the exact amount is a judgment call that also depends on your face shape, layering, hair texture and the finished look you want. Professional stylists treat grams as a starting point, not a fixed prescription. Use the range as a guide, and confirm with your stylist or the brand before ordering, especially for a first install.
Where will 18, 20 or 24 inch hair extensions fall?
Measured straight down the back, about 14 inches reaches the shoulders, 18 inches the upper back, 20 to 22 inches the mid-back, 24 inches near the waist, and 26 inches and longer toward the hips. Where it lands depends on your height and torso, so taller people see the same length sit a little higher. Set your height in the calculator for a closer estimate.
How much do hair extensions cost?
Human-hair extensions typically cost about $50 to $150 per pack or bundle, so a full head of 2 to 4 packs runs roughly $150 to $500 for the hair, plus a salon fitting fee of about $100 to $400 depending on the method and your area. Clip-ins are cheapest (you fit them yourself); sew-ins, tape-ins and keratin bonds add install time. Use the cost calculator above with your own prices for a tailored estimate.
How long is 20 inch hair?
On an average height of about 5'4" to 5'6", 20 inch hair falls around the mid-back, a few inches below the bra strap. Taller frames carry the same length a little higher. Because length is measured straight down the back, curly or wavy hair looks 1–2 inches shorter, so allow for shrinkage. The length chart above maps every length from 12 to 30 inches to where it lands.
How long is 16 inch hair?
About 16 inch hair usually sits just below the shoulders, around the collarbone or the top of the bust at the front. It is a popular first length because it adds noticeable body with easy upkeep. Lengths are measured in a straight line, so curly textures look a couple of inches shorter. For reference, 14 inch reaches the shoulders and 18 inch reaches the upper back.
How long is 24 inch hair?
Around 24 inch hair reaches the waist on most people of average height, for a dramatic long look. Because the same weight of hair is stretched over more length, 24 inch installs usually need more grams — about 180 to 220 grams for a full head — to stay thick to the ends. Taller frames see it sit a little higher, and 22 inch lands just above at the lower back.
How much are hair extensions at a salon?
At a salon you pay for both the hair and the fitting. The hair is usually $150 to $500 for a full head, and professional installation adds roughly $100 to $400 depending on the method. Clip-ins are cheapest since you fit them yourself, while tape-ins, keratin bonds and sew-ins take more chair time. Use the cost calculator above with your own prices for a tailored total.
How many micro-link or micro-bead extensions do I need?
Micro-link, micro-bead and i-tip extensions are applied strand by strand with small beads, at roughly 1 gram per strand. A full head is usually about 100 to 200 strands (150 to 200 grams), with fine hair needing fewer and thick or long hair needing more. Choose Micro-link in the method menu and the calculator converts your gram estimate into strands and packs.