String Pattern and Tension
Short answer: A string pattern such as 16x19 counts the mains by the crosses. According to the International Tennis Federation (ITF), wider string spacing and a larger head both make the stringbed more flexible at the same tension, so a dense 18x20 strung at the same reference tension as an open 16x19 tends to feel firmer. No source we use publishes a pound adjustment for pattern, so start inside the range printed on each frame, change one thing at a time, and compare each racquet only with its own fresh-string baseline.
What a string pattern is
A string pattern gives the number of main strings (the long ones running from throat to tip) by the number of cross strings. A 16x19 racquet has 16 mains and 19 crosses. Patterns with fewer strings, such as 16x19, are called open; patterns with more, such as 18x20, are called dense.
The pattern does not work alone. The same count spread across a larger head leaves wider gaps and longer strings, so head size and pattern together decide how far apart the strings sit. The ITF’s Rules of Tennis also require the hitting surface to be a pattern of crossed strings, alternately interlaced or bonded where they cross, which is what limits how far strings can slide.
How pattern and head size change stringbed stiffness
The ITF describes stringbed stiffness as depending on tension and on the arrangement of the strings. If the space between strings increases, the face becomes more flexible; if the strings get longer, for example in a larger head, stiffness falls.
| Factor | More flexible stringbed | Stiffer stringbed | Evidence |
|---|---|---|---|
| Pattern | Open (wider spacing), e.g. 16x19 | Dense (tighter spacing), e.g. 18x20 | ITF technical guidance |
| Head size | Larger head, longer strings | Smaller head, shorter strings | ITF technical guidance |
| Reference tension | Lower | Higher | ITF technical guidance |
| String | Softer string | Stiffer string | Tennis Warehouse University laboratory testing |
The ITF also explains what a more flexible stringbed does. The face distorts more on impact, the ball deforms less and the ball stays on the strings longer. That longer contact spreads a smaller force over more time, which reduces impact shock, but the ITF lists all three effects as reasons a softer stringbed can cost control. Lower tension also returns slightly more ball speed: the ITF puts a 25% drop in tension at about a 2% gain in groundstroke speed.
Does an open string pattern give more spin?
In Tennis Warehouse University laboratory tests by Rod Cross and Crawford Lindsey, more open patterns allowed more string movement and produced more spin. A related test series found that string movement and snapback correlate very strongly with spin, and that polyester moved more than nylon or gut. The authors are clear that the main contributors to spin are the speed and angle of the swing, not the equipment.
Tension is a weaker lever than most players expect. The ITF reports no appreciable difference in spin between low- and high-tension strings. Racquet makers design for string movement too: Babolat describes the Pure Aero 98’s 16x20 pattern and grommets as optimising string movement for spin, which is a manufacturer’s claim rather than an independent test.
For the full evidence on spin and tension, read the best tennis string tension for spin guide.
Choosing a tension for your pattern
Start with the range printed on the frame. For example, Babolat publishes 46–55 lbs (21–25 kg) for the 16x20 Pure Aero 98. The tension calculator intersects that printed range with the starting range for your string type. It asks for pattern and head size as context but, like the sources above, does not add or subtract pounds for them.
The rules below are String Tension AI’s reading of the stiffness mechanism. They are directions to test, not published adjustments:
- Moving from an open to a dense pattern at the same reference tension, expect a firmer stringbed. If you want the old feel, try one small step lower inside the new frame’s range.
- Moving from a dense to an open pattern, expect a softer, livelier stringbed. If it feels hard to control, try one small step higher inside the range.
- Moving to a larger or smaller head, apply the same logic: a larger head is softer at the same tension, a smaller head firmer.
- Changing racquet and string together makes the result hard to read. Keep the string and gauge the same for the first string job in a new frame.
Material and gauge move the result too. See tennis string types explained for how material sets the starting range, and the tennis string gauge guide for what thickness changes.
Comparing readings across racquets
Because pattern and head size change the stringbed, two racquets strung at the same reference tension are not the same setup, and their readings are not interchangeable. A useful comparison stays within one racquet:
- Take a baseline for each racquet soon after stringing, using the routine in our measurement guide.
- Compare later readings with that racquet’s own baseline, for example with the racquet tension checker, which shows the change in lbs, kg and percent.
- Record the pattern and head size with each string job, so a different feel in another frame is not mistaken for a tension change.
Terms such as mains, crosses and stringbed stiffness are defined in the tennis stringing glossary.
String pattern and tension: FAQ
Should I string an 18x20 racquet lower than a 16x19?
Not by a fixed amount. The ITF explains that tighter string spacing makes the stringbed stiffer at the same tension, so a dense pattern tends to feel firmer, but no source we use publishes a pound adjustment. Start inside the range printed on the frame, and if a dense pattern feels too firm, try one small step lower in a later string job.
Does a bigger head size need a different tension?
A larger head has longer strings, which the ITF says lowers stringbed stiffness at the same tension, so it tends to feel softer. Use the range printed on that frame as your starting point rather than adding or subtracting a fixed amount for head size, and compare the racquet with its own fresh-string baseline.
Does an open string pattern give more spin?
In Tennis Warehouse University laboratory tests, more open patterns allowed more string movement and produced more spin. The researchers stress that swing speed and swing angle contribute more to spin than the equipment, and the ITF reports no appreciable spin difference between low- and high-tension strings.
Can I compare tension readings between two racquets?
Not directly. Pattern and head size change the stringbed, so two racquets strung at the same reference tension are different setups. Take a baseline reading for each racquet after stringing and compare later readings only with that racquet’s own baseline.
What the sources support
The ITF document supports how spacing, head size and tension change stringbed stiffness, the control and ball-speed trade-offs, the interlacing rule, and the absence of an appreciable spin difference by tension. Tennis Warehouse University’s laboratory tests support the links between open patterns, string movement and spin, and between string stiffness and stringbed stiffness. Babolat’s product page supports one frame’s pattern and printed range and its own design claim. The decision rules and the comparison routine are String Tension AI’s method.
Accessed October 3, 2026
- International Tennis Federation — Rackets and Strings: Strings (November 2019) for string spacing, head size, tension and stringbed stiffness, control and ball speed, rule 4a, and spin by tension (governing-body technical guidance).
- Tennis Warehouse University — String Patterns and Spin (Rod Cross and Crawford Lindsey, January 30, 2013) for open patterns, string movement and spin (laboratory testing).
- Tennis Warehouse University — String Snap-Back and Spin for string movement, snapback, material and the larger role of the swing (laboratory testing).
- Tennis Warehouse University — String Stiffness for stiffer strings making a stiffer stringbed at the same tension (laboratory testing).
- Babolat — Pure Aero 98 product page for its 16x20 pattern, 46–55 lbs (21–25 kg) recommended tension and string-movement design claim (manufacturer specification).
Give every racquet its own baseline
Measure each racquet fresh after stringing, then track it against its own baseline instead of comparing frames with different patterns.
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