A vise is measured primarily by its jaw width, which is the horizontal distance across one jaw face. This single number is how vises are sold and compared, so a “6-inch vise” has jaws that are 6 inches wide. But jaw width alone doesn’t tell you everything you need to know. To fully measure a vise, you also need its maximum opening, throat depth, and mounting dimensions.
Jaw Width: The Primary Measurement
To measure jaw width, close the jaws completely and measure the horizontal distance across the face of one jaw from left edge to right edge. This is the number stamped on the vise or listed in product specs. Common sizes range from 3 inches for light-duty work up to 8 inches or more for heavy industrial use.
Jaw width tells you how much surface contact the vise has on your workpiece, but it doesn’t directly indicate overall size, clamping force, or how far the jaws open. A quality 4.5-inch vise can handle the vast majority of home shop and garage tasks. Many people assume they need a 6-inch model when a smaller, better-built vise would serve them just as well. A Wilton 600S, for instance, has 6-inch jaws but weighs 155 pounds, which is far more vise than most hobbyists need or have bench space for.
Maximum Opening Capacity
Maximum opening is the distance between the two jaw faces when the movable jaw is cranked as far back as it will go. This tells you the largest workpiece you can clamp. To measure it, open the vise fully until the screw is still engaged by at least one full turn, then measure the gap between the inner faces of the jaws. Don’t crank the screw until it nearly disengages, because that gives you a number you can’t actually work with.
Maximum opening varies significantly between brands and styles, even among vises with the same jaw width. A pattern-maker’s vise, designed for gripping large pieces of wood, typically opens 50% to 80% wider than a standard bench vise of the same jaw width. So if you’re replacing a vise or shopping for one, check the opening capacity separately rather than assuming it scales with jaw width.
Throat Depth
Throat depth is the vertical distance from the top edge of the jaws down to the top of the slide (the horizontal rail the movable jaw rides on). This measurement determines how tall a workpiece can extend down below the clamped area. A deeper throat gives you more clearance for holding irregularly shaped or tall objects.
To measure throat depth, close the jaws and measure straight down from the top of the jaw to the top surface of the slide bar. On an 8-inch industrial vise, throat depth might be around 4 inches. On smaller vises, it could be 2 to 3 inches. If you regularly clamp sheet metal, plates, or anything that hangs below the jaws, this dimension matters more than jaw width.
Mounting Bolt Pattern
If you’re replacing a vise or mounting one to a new bench, you need to measure the bolt hole pattern on the base. Vise bases have either three or four mounting holes arranged in a pattern, and manufacturers specify this as a bolt circle diameter, which is the diameter of an imaginary circle that passes through the center of each bolt hole.
To measure this yourself, find the center of one bolt hole, then measure the straight-line distance to the center of the hole directly opposite it. That distance is the bolt circle diameter. For smaller vises (4 to 5 inch jaw width), bolt circle diameters typically fall between 7 and 9 inches, with bolt holes sized for 7/16 or 1/2-inch bolts. Larger vises (6 to 8 inch jaws) have bolt circles around 9 to 10 inches and use 1/2 or 5/8-inch mounting bolts.
Also measure the bolt hole diameter itself so you can drill your bench correctly. Use a caliper or simply try to pass a known bolt size through the hole.
Pipe Jaw Capacity
Many bench vises have a set of curved pipe jaws built into the body, below the flat main jaws. These are measured by the range of pipe diameters they can grip. A typical 8-inch bench vise with integrated pipe jaws handles pipe from 1/4 inch up to 3 inches in diameter. To check your vise’s pipe capacity, place a round object in the pipe jaws and see what fits securely. The curved surfaces should contact the pipe on both sides without the flat jaws touching first.
Checking for Wear and Backlash
If you’re evaluating a used vise, one important measurement is backlash, which is the amount of play or dead movement in the screw mechanism. Clamp a piece of wood or metal lightly, then start turning the handle to loosen. Count how far the handle rotates before the jaws actually begin to move. On a vise in decent condition, you might see 10 to 30 degrees of handle rotation before anything happens. A worn vise can have 90 degrees or more of dead play, which makes precise clamping frustrating.
You should also close the jaws completely with nothing between them and check for gaps. Hold the vise at eye level and look for light passing between the jaw faces. On a quality vise, the faces should meet evenly across their full width. Uneven contact means the jaws or slide are worn, and the vise will struggle to hold small or thin workpieces securely.
What Size Most People Actually Need
For general garage and home workshop use, a 4 to 5 inch jaw vise covers nearly everything: grinding, filing, holding parts for drilling, light welding, and assembly work. A 4.5-inch quality vise will outperform a cheap 6-inch vise in both clamping force and durability. Bigger jaws also mean a heavier vise and a larger footprint on your bench, so measure your available bench space and thickness before choosing. Most vises need a bench edge that’s at least 2 to 3 inches thick to mount securely, and you’ll want several inches of clearance behind the vise for the screw housing when the jaws are fully open.