Tennis head size: square inches, cm² and racket length

A tennis racket labelled with a 100-square-inch head is not 100 inches long. Yet a short listing can place “100”, “645” and “27” next to one another with little explanation. Those figures become useful only when you keep their headings and units attached.

Head-size comparisons involve area. Racket length is a separate linear measurement. This guide explains the unit conversion and the difference between calculated values and published specifications, so you can resolve an unclear listing without treating every numerical mismatch as a different racket.

Keep square units separate from length

The LTA's racket guide lists head sizes in square inches and square centimetres, while its racket-size chart uses inches for length and includes a 27-inch adult entry. The shared word “inch” does not make these the same kind of measurement.

The small raised 2 in in² or cm² means “squared”. You may also see “sq in” or “sq cm”. Keep that notation when copying a specification into your notes. Writing “head: 100 inches” loses the distinction between area and length.

Likewise, a length measurement cannot confirm a head-area figure. Multiplying the overall racket length by a width would describe a rectangle using those dimensions, not establish the area specified for its head. Use the manufacturer's head-size entry rather than inventing a measurement method from a photograph.

Convert the area with the correct factor

The NIST area-conversion table gives 1 square inch as exactly 6.4516 square centimetres. Multiply an in² value by 6.4516 to express that same area in cm². Converting the unit changes the number, not the amount of area.

These examples show arithmetic only. They are not measurements of particular rackets, and the extra decimal places do not establish a manufacturer's production precision.

Area conversions: final column rounded to one decimal

in²	Exact cm²	Rounded cm²
98	632.2568	632.3
100	645.1600	645.2
105	677.4180	677.4

For example, 100 × 6.4516 gives 645.16. Dividing 645.16 by the same factor returns 100. Keep the unrounded result while checking your calculation, then state any rounding used in the displayed answer. Do not silently switch between a whole-number label and a multi-decimal calculation.

Read a published pair as a specification

Wilson's US Open 2026 Clash 100 V3 page, model WR21600, lists head size as 645 sq cm / 100 sq in. It lists the 16 × 19 string pattern separately. This is a named example of how a manufacturer presents the fields, not a recommendation to buy that model.

The listed 645 is consistent with rounding the calculated 645.16 to the nearest whole square centimetre. That observation does not tell us Wilson's actual measurement or rounding procedure. Nor does it prove that a physical racket's head measures exactly either displayed figure.

If another listing gives a different pair, check the exact model and the source before deciding why. A mathematical conversion can reveal a question to ask; it cannot establish a manufacturing tolerance, identify a counterfeit or resolve an unexplained product revision.

Build a comparison that keeps the labels

Consider a fictional advertisement reading “head 100; length 27”. Ask for three details: the exact model and version, the full head-area value with its unit, and the length with its unit. Familiar numbers are clues, not confirmation. Leave an absent unit unresolved until the seller or model documentation clarifies it.

Record the published specification separately from your calculated conversion. For the Wilson example, one note could preserve “645 sq cm / 100 sq in” as listed; another could record “100 in² converts to 645.16 cm²”. These notes have different purposes and can coexist without claiming the physical item was measured.

Matching head-area labels also do not establish identical head shape, string counts or weight. Our string-pattern guide explains mains and crosses, while our weight and balance guide separates the other measurement fields. Keep those checks alongside head size rather than using one number to describe the whole setup.

Practical takeaway

Copy the heading, value and unit together. Convert area using an area factor, state your rounding, and distinguish the calculation from the manufacturer's label. An unclear specification needs clarification, not a guessed unit or a performance promise.