How to Measure a Windshield Chip or Crack

Measure three things: the size of the break twice (the solid core, then tip to tip across the longest legs), the length of any crack along its path, and where it sits (distance to the true glass edge, and whether it is inside the driver's zone). Then check them against the rulebook that will judge them: the repair standard, a state inspector and a federal truck inspector each measure differently, and a break that passes one can fail another.

Legs in or legs out: why both answers are going around

Drivers measure the round core; shops measure tip to tip. Both numbers appear in the rules.

The industry repair standard, ANSI/AGSC/NWRD/ROLAGS 002-2022 (approved December 8, 2022), uses the core-only number in exactly one place. A combination break, which it defines as "damage with multiple characteristics, i.e., star within a bullseye, short or long crack(s) emanating from the damage," is repairable with a "diameter of body (excluding legs) not to exceed 2 inches (50 mm)." Everywhere else the legs count: a star is limited by the "diameter of the break," and the driver's zone by the "diameter of damage," with no exclusion. The federal truck rule counts "any damaged area which can be covered by a disc," so a leg poking out from under the disc fails it.

So tip to tip decides almost every case. Write both down. The shapes themselves are sorted out in bullseye or star break, and the full catalog is in windshield damage types.

What to measure with, and how close each stand-in gets

A steel ruler with 1/16 inch marks is best. Without one, several things in your pocket land almost exactly on the thresholds that matter.

Coin sizes are the US Mint's circulating specifications; the card size is the ISO/IEC 7810 ID-1 format used for bank cards and licenses.

How to measure a chip in six steps

1. Clean and dry the spot. Wipe around the break, not into it. Water hides legs.
2. Find every leg with raking light. Hold a flashlight almost flat to the glass and move it around the break. Hairline legs flash silver.
3. Measure the core. Lay the ruler flat across the dark round body, ignoring the legs. This is the number for the 2 inch combination limit.
4. Measure tip to tip. Turn the ruler until it spans the two leg tips farthest apart. This is the number for every other limit.
5. Check the pit. Run a fingernail over the impact point. ROLAGS says do not repair "damage with a pit size greater than 3/8 inch (9 mm)," and in the driver's zone the finished pit must be no greater than 3/16 inch (5 mm).
6. Look from inside. Run a fingernail over the same spot on the inside face. ROLAGS rules out "damage on the inside lite (layer)" and damage that "penetrates both the inside and outside layer." What that looks like is in inner ply damage.

How to measure a crack: length, ends and which edge

• Length. Measure along the curve with a string or flexible tape. None of the rule texts below says which way to measure, so take the longer number. ROLAGS calls a crack of 6 inches (150 mm) or less a short crack, more than 6 inches a long crack, and sets the repairable limit at "no longer than 14 inches (350 mm)." Whether a shop near you takes on long cracks is covered in long crack repair.
• Ends. ROLAGS defines an edge crack as "any crack that extends to an edge" and a floater as one that does not. It says do not repair "edge crack(s) that intersect more than one edge."
• Origin. A crack that "extends from an edge and lacks an impact point" is a stress crack under ROLAGS, and stress cracks are on its do not repair list. Telling the two apart is in stress cracks versus impact cracks.

Put dated tape just beyond each tip. If the crack passes it within a week it is growing; what makes a crack spread explains the urgency.

Position: the true edge, the driver's zone and the inspector's lines

Each rulebook draws its lines from a different reference point.

• Distance to the edge. Measure to the real edge of the glass, which sits under the moulding, not to the inner line of the black border. The border can hide an inch or more (see what the black frit band hides). The familiar "nothing within 2 inches of the edge" is shop and insurer practice; ROLAGS sets no distance. Why shops hold to it anyway is in edge cracks.
• The ROLAGS driver's zone. The driver's primary viewing area is "12 inches wide," "centered on the driver's position," and extends "from the top to the bottom of the wiper sweep." Find the point straight ahead of the steering wheel center and tape 6 inches to each side. What the tighter limits inside it mean is in repair in the driver's line of sight.
• The federal truck zone. 49 CFR 393.60(c) protects the glass "upward from the height of the top of the steering wheel," excluding a 2 inch (51 mm) border at the top and a 1 inch (25 mm) border at each side. Below the top of the wheel it sets no damage limit.
• State lines. Virginia measures its 3 inch line up "from the junction of the dash board and the windshield." Pennsylvania's acute area sits "directly in the driver's normal line of vision, 8 1/2 inches wide and 5 1/2 inches high."

The same windshield under six rulebooks

Every measured limit in the repair standard, the federal truck rule and three state inspection programs. A blank means no number is set.

Run one break through it: a bullseye with a 1/2 inch core and one leg, 1 1/4 inches tip to tip. Under ROLAGS it is a combination break with a body under 2 inches, so it is repairable outside the driver's zone and not inside it, being over 1 inch. On a truck it fails, because it will not fit under a penny. In Virginia it passes, being under 1 1/2 inches. In New York it passes, being well under 3 inches. In Pennsylvania it turns on whether it falls inside the 8 1/2 by 5 1/2 inch area. Each state's wider rules are on the Virginia, New York and Pennsylvania pages, and the truck rules in commercial vehicle glass rules.

Whose number wins when the shop, the insurer and the inspector disagree

• The inspector applies the state rule only, and only where the state inspects (see which states inspect glass).
• The shop can be stricter than ROLAGS but should not be looser. One that declines a break inside the ROLAGS limits is applying its own policy; a second shop may take it.
• The insurer routes the claim by what the shop reports, so have your measured photo ready (see filing a glass claim).

With several breaks, spacing matters too: ROLAGS wants 4 inches between repairs inside the driver's zone, the truck rule 3 inches between any damage. See how many chips one windshield can take.

Where these measurements stop deciding

A size inside every limit can still be a replacement. ROLAGS also rules out damage with "visible impurities that cannot be removed through cleaning," damage to the plastic interlayer, three or more long cracks from one impact point, and damage where "value-added features may be negatively affected," such as a rain sensor or heads up display zone. ROLAGS is a voluntary industry standard, not a law, and state inspection rules are amended from time to time, so check your state's current text before relying on a threshold.

What to do next

Write down core size, tip to tip size, crack length and distance to the true edge, and whether the break is inside your 12 inch zone. Put them into the repair or replace tool, or into the damage identifier if you are unsure what type it is. If the answer is repair, expect roughly $60 to $150 cash for the first chip (see what chip repair costs),. If it is borderline, whether your windshield can be repaired covers the factors beyond size, and the damage section covers the rest.

Frequently asked questions

Do you include the legs when measuring a windshield chip?

Usually yes. The repair standard excludes legs only for a combination break, whose solid body may be up to 2 inches. A star break is measured across the whole break, any damage in the driver's 12 inch zone is limited to 1 inch overall, and the federal truck rule requires the whole damaged area to fit under a 3/4 inch disc. Record both the core and the tip to tip size.

Is a chip smaller than a quarter always repairable?

No. A quarter is 0.955 inch across, so damage it covers meets the 1 inch size limit for a bullseye. But the chip can still be ruled out by its position or depth: damage on the inside layer, a pit bigger than 3/8 inch, contamination that will not clean out, or a spot over a rain sensor or heads up display zone all point to replacement whatever the size.

How do I find the driver's primary viewing area on my car?

Sit normally in the driver's seat and find the point on the windshield straight ahead of the center of the steering wheel. Put a strip of tape 6 inches to each side of that point. The zone between the strips, from the top to the bottom of the wiper sweep, is the 12 inch wide area the repair standard treats strictly. Damage there must be 1 inch or less to repair.

Should I measure a crack in a straight line or along its curve?

Along the curve. The repair standard and the inspection rules give crack lengths without saying how to measure them, so use the longer reading. Lay a string or flexible tape along the crack from tip to tip and measure that. Mark both tips with dated tape so you can tell in a week whether the crack is still growing.

Where is the edge of the windshield when I measure edge distance?

At the real edge of the glass, which is hidden under the moulding, not at the inner line of the black ceramic border. The border and trim can cover an inch or more, so measuring to them makes damage look farther from the edge than it is. If you cannot find the true edge, treat the start of the black border as the edge and allow an extra inch.