Hair bundles explained: how length is measured, how many you need, and how to care for them

1. How length is measured

Hair length is quoted stretched straight. One seller’s measuring guide says curly and wavy hair should be stretched straight when you measure it, and adds that the figure is taken by hand, so a small inaccuracy of 0.1 to 0.3 inch is to be expected.

Retailers describe wig and bundle length the same way: from the weft (or the crown, for a wig) to the ends, with the hair pulled straight. The consequence is that the same labelled length looks shorter on curly hair. One retailer’s guide estimates that waves sit about 2 inches shorter than straight hair at the same measurement and curly textures about 4 inches shorter, and suggests ordering about two sizes up for curly textures. These are a retailer’s estimates, not laboratory measurements, so use them as a rough guide.

Practical point: check whether a listing states the length as stretched. If it does not, ask the seller before you buy.

2. How many bundles to plan for

Sellers publish their own tables of how many bundles a full head needs at each length. One seller’s table, for lengths from 8 to 28 inches, recommends:

That seller adds that one bundle normally weighs 95 to 100 g, that 3 to 4 bundles suit a full head, and that 4 are necessary from 20 to 30 inches. Tables from other sellers differ, so treat any count as a rule of thumb.

The number to check is grams, not bundles. Three 100 g bundles is about 300 g; three 50 g bundles is 150 g. Bundle weights vary by brand, so confirm the weight per bundle in the listing, then divide the weight you need by it.

3. Texture and combing

One seller’s care guide recommends a wide-tooth comb for straight and body wave bundles and says loose wave, deep wave and curly bundles can’t be combed, adding that more tightly curled hair needs extra care when washing to avoid tangling.

The caution against combing curly hair dry agrees with dermatologists. The American Academy of Dermatology says brushing dry curly hair can cause breakage and frizz. For curly and coily hair its advice is to detangle while the hair is wet, with a leave-in conditioner, using fingers or a wide-toothed comb or brush made for curls, working in sections. Its general guidance for wet hair is a wide-tooth comb, starting at the ends and working upward.

Those recommendations describe natural hair on a scalp. Loose bundles and wefts have no scalp oils, so the safest course is to follow the care sheet that comes with the bundles, and to keep to finger-detangling for the curlier textures.

4. Washing and drying

One seller’s eight-step care guide runs: wet the hair with warm water; soak it with a mild shampoo for a few minutes; rinse with clean water; use a towel to wipe the water off; avoid too much effort wiping the tail; comb curly hair gently with your fingers; sort out the hair a few times without a comb; and hang the weft open to air-dry so curls hold well.

Dermatologists’ general advice agrees on the main points: use a gentle shampoo and conditioner, wrap hair in a towel or t-shirt to absorb water and avoid rough rubbing, comb wet hair with a wide-tooth comb from the ends upward, and limit heat. The academy’s pages do not cover loose bundles, so for those, follow the care sheet that comes with them.

If the hair is installed (a sew-in or similar), the picture changes, because the style then affects your own hair and scalp. The American Academy of Dermatology advises having it fitted by a professional; asking for it to be loosened if it causes pain or headaches, since constant pulling can lead to a permanent form of hair loss called traction alopecia; removing clip-in extensions before washing your own hair; and limiting wear to two or three months at most before a break. See a board-certified dermatologist if hair breaks or falls out.

5. Heat and restyling

One seller’s restyling guidance says not to exceed 180 °C and not to restyle too often, so the hair lasts longer.

That limit is cautious. A 2011 paper in the Journal of Cosmetic Science notes that hot flat irons can exceed 200 °C and cause significant damage to hair keratin; its experiments used 232 °C, and its authors note limited research at those temperatures. The American Academy of Dermatology gives no temperature figure, but advises low or medium heat settings with a heat-protectant product, flat irons on dry hair no more often than every other day, and curling irons held in place for only a second or two.

Two cautions. This research concerns human hair; synthetic fibres have different limits, so follow the temperature stated for the product. And “heat-resistant” means a stated limit, not that heat is harmless.

6. A word on the “identification test”

The same seller’s guide describes a burn test. It says synthetic hair hardens into a plastic-like mass after burning, while real hair becomes a powder that can be crushed, and a cosmetology study guide describes a similar pattern.

PowderedPurple has not tested this and does not walk through it: it involves an open flame, fumes and, with synthetic fibre, molten drips. It also tells you less than it seems to. At best it points to protein or plastic, not to where hair came from, how it was processed or how good it is, and a blend can give a muddled result.

A safer route is to ask the seller for the stated fibre content in writing and to compare it with the listing.

7. A short checklist before you buy

• Is the length stated as stretched? If not, ask.
• What is the weight per bundle, and how many grams does your look need?
• What is the stated fibre (human hair, synthetic or blend), and is it in writing?
• What heat limit and care instructions does the seller give?
• Is the texture one you are prepared to detangle by hand?
• For installed styles, how will it be fitted, and for how long will you wear it?

Related on this site

Browse bundle, extension and wig listings in the wigs and hair extensions catalogue. Product facts on those pages are the seller’s, shown as supplied, and we have not tested the products. See also our guides to glueless wigs and shampoo surfactants.