How to Calculate How Much Hair Your Client Needs: A Gram-by-Gram Guide for Stylists

One of the most common ordering mistakes salons make is guessing at hair quantity. A client comes in, you eyeball the density, order what feels right, and either end up short mid-install or with two bundles sitting in your drawer for three months. Both cost you money.

Hair extension quantity is calculable. It is not an art form. Once you understand the variables, you can hit the right gram count almost every time, across every method.

This guide covers how to calculate grams for the three most common salon extension methods: tape-in, weft (including genius weft), and k-tip/i-tip bonds.

The Two Variables That Actually Matter

Before you look at any gram chart, understand what drives quantity:

Hair density is how much natural hair the client has. Not just the thickness of individual strands, but the number of active follicles on the scalp. A client can have coarse hair with low density, or fine hair with high density. You need to assess both separately.

Target length is not the client’s current length, but the length they want to reach, and how much of that length needs to be filled. A client adding 4 inches of length to a full-density head needs far less than a client adding 4 inches to a low-density head.

A third factor worth noting: the drawing level of the hair itself. Double drawn hair, where shorter strands are removed, will feel and install thicker per gram than single drawn. If you are working with single drawn hair, increase your gram count by roughly 20 to 30 percent to achieve the same result. If you recently switched suppliers or drawing levels, recalibrate before your next order.

Grams by Method: Actual Ranges

Tape-In Extensions

Tape-in extensions typically come in 50g packs, with approximately 20 wefts per pack. Here are realistic ranges by head density for a full-head application:

Density	Grams Needed	Packs
Fine / low density	100-150g	2-3 packs
Medium density	150-200g	3-4 packs
Thick / high density	200-250g	4-5 packs

These figures apply to adding length. If you are doing a volume install only, with no added length, subtract one pack from each tier. If the client is getting root-to-tip blending across the full head, add one pack.

The tape sandwich method uses two wefts per application section. At 20 wefts per 50g pack, a 200g order gives you 80 individual wefts, or 40 tape sandwiches. Keep that math in mind when estimating placement sections during your consultation.

Genius Weft and Hand-Tied Weft

Weft extensions are measured by weight and installed in rows. A full-head install typically uses 3 to 4 rows, depending on head size and the density goal.

Density	Grams Needed
Fine / low density	100-150g
Medium density	150-180g
Thick / high density	180-250g

Genius weft runs narrow, typically 0.5 to 1cm in width, so each weft row is made up of multiple pieces placed side by side. The weight per row depends on the length ordered. A 20-inch row at medium density runs about 30 to 40 grams. Multiply by the number of rows to estimate your total weight before ordering.

One note on weft length: if your client has a narrow nape or a noticeably tapered head shape, account for shorter wefts at the lower rows. Cutting down a weft is standard practice, but you are still paying for the hair you trim off. Some suppliers offer shorter weft lengths at a corresponding lower price – worth asking about if your client base skews narrow-nape.

K-Tip and I-Tip Bonds

Bond extensions are counted per strand, not by gram weight. Most suppliers package them in 100-strand packs, at approximately 50 to 55 grams per pack for 18 to 22-inch lengths.

Density	Strands Needed
Fine / low density	100-125 strands
Medium density	125-175 strands
Thick / high density	175-225 strands

For context: a full k-tip install on a medium density client runs about 150 strands and takes 2.5 to 3.5 hours in the chair. This is why k-tips command a higher service price, regardless of the hair cost itself.

Each strand weighs approximately 0.5 grams before the bond. At 150 strands, that is about 75 grams of actual hair, plus bond material. When comparing prices across suppliers, make sure you are looking at strand count and gram weight together, not just one figure. A lower per-strand price on a lighter strand is not necessarily the better deal.

How to Assess Client Hair Density Before Ordering

You need a consistent method to evaluate each client. Here is a practical three-part check that takes less than two minutes:

Part width test: Pull a horizontal part across the crown. If you can see scalp clearly between strands, the client has low density. If the scalp is barely visible, density is medium to high.

Ponytail circumference: Ask the client to pull a low ponytail at the nape and measure the circumference. Under 2 inches is fine or low density. 2 to 3 inches is medium. Over 3 inches is high density.

Strand width comparison: Hold a strand of the client’s hair beside a reference strand from your sample kit. Coarse strands are roughly twice the diameter of fine strands. This tells you about strand texture, not total density, but both matter when selecting method and gram count.

Write the assessment result in the client file. Over time you build a reference set for how your typical client base lands, and ordering becomes faster and more accurate.

Common Calculation Mistakes

Ordering for current length, not target length. The gram count for a client going from 12 inches to 20 inches is not the same as a client going from 16 to 20 inches. Longer target lengths require more hair to blend the transition zone, particularly if the client’s natural hair has significant taper at the ends.

Not accounting for layers. Heavily layered haircuts require more extension rows to blend properly. A client with significant internal layering may need 20 to 30 grams more than the base calculation suggests. When in doubt, err toward the higher end of the range and trim down.

Assuming all gram weights are equal across suppliers. A 150g single drawn pack and a 150g double drawn pack at the same length will install completely differently. The double drawn will look fuller with the same gram count. If you switch suppliers or drawing levels, recalibrate before committing to a full order.

Over-applying tape-ins on fine hair. More product does not always mean better coverage on low-density hair. Fine hair has a weight tolerance limit. Overloading it causes tension at the root and accelerated shedding. For fine-density clients, targeted placement beats quantity every time.

Forgetting to account for grows-out in advance orders. If you are pre-ordering for a client’s next appointment 6 to 8 weeks out, factor in that their natural hair will have grown. Tape-in clients in particular may need slightly different weft positioning than the current install, which can affect quantity.

Ordering for Inventory vs. Per-Client Orders

If you are stocking hair rather than ordering per client, the math shifts. Build inventory around your median client profile. For most salons, that is medium density, 16 to 20-inch target length.

Stock levels that work for a medium-volume salon running 15 to 25 extension clients per month:

• Tape-in: 4 to 6 packs per color in core shades, 2 to 3 packs in accent shades
• Weft: 3 to 4 bundles per core color at 18 and 22-inch lengths
• Bond: 300 to 400 strands per core color

Core shades typically cover 70 percent of your clients. Identify your most-ordered 5 to 6 colors over 3 months and anchor your stock there. Order everything else on demand to avoid color-rotation waste.

Track What You Actually Use

The cleanest way to refine your ordering over time is to track installation records by client. Note the method, the gram count used, how much was trimmed off, and the client’s satisfaction at their next appointment. After 20 to 30 records, patterns will emerge.

You may find your assessments consistently run 15 percent under for clients with layered cuts, or that your high-density clients are actually landing in the medium-density calculation range. This data is worth more than any general chart because it reflects your specific client base and your specific supplier’s hair weight standards, which vary between manufacturers.

Salon owners who track this data typically reduce over-ordering by 20 to 30 percent within their first year and eliminate the “short on hair mid-install” problem almost entirely. The tracking does not have to be complex – a simple spreadsheet with six columns is enough to start generating useful patterns.