To measure your boat for a cover, you'll measure the centerline length from bow to stern in a straight line, measure the beam at the widest point, and account for any accessories like outboard motors or swim platforms. These three measurements determine whether you need a universal-fit, semi-custom, or guaranteed-fit option like a MasterCraft X2 boat cover.
This guide is for boat owners who want a cover that actually fits without sagging, letting in moisture, or tearing at the seams. If you've been burned by a cheap cover that didn't match your boat's dimensions, check out our MasterCraft boat cover replacement for a precise fit.
Here's what we'll cover:
- The three measurements every boat owner needs
- How to account for windshields, outboard motors, and other add-ons
- When to choose semi-custom versus guaranteed-fit covers
- Common measuring mistakes that lead to poor fit
Step 1: Measure Your Boat's Centerline Length
Centerline length is the distance from the tip of the bow to the farthest point of the stern, measured in a straight line. This is the single most important measurement for boat covers, and it's where most mistakes happen.
Start at the very front of the bow. Run your tape measure straight back to the stern along the center of the boat. Don't follow the curve of the hull. Don't measure over the windshield or bimini top. Don't measure along the deck. Measure in a flat, straight line as if you're drawing a ruler from bow to stern.
If your boat has a swim platform or outboard motor that extends past the hull, decide whether your cover will go over it or stop at the transom. Most mooring covers and storage covers are designed to accommodate outboard motors and swim platforms. If that's your setup, measure to the end of the platform or motor. If you're covering just the hull, measure to the transom.
Write down your measurement in inches. Most boat covers are sized in one-foot increments, so a boat that measures 202 inches (16 feet, 10 inches) would typically use a 17-foot cover. Don't round down. Fabric that's too short leaves your bow or stern exposed.
Step 2: Measure the Beam at the Widest Point
Beam is the width of your boat at its widest point. For most V-hull runabouts, that's somewhere near the middle of the boat. For pontoons, it's the outside edge of one pontoon to the outside edge of the other.
Run your tape measure straight across the boat at the widest section. Measure from the outermost point on one side to the outermost point on the other. Include any railings, rub rails, or fenders that stick out beyond the hull. Your cover needs to fit over everything, not just the fiberglass.
If your boat has a bimini top that folds down, measure with it folded. If it doesn't fold, measure to the widest point of the frame. Some covers are designed to fit over standing bimini tops, but you'll need to know that width before you order.
Write down your beam measurement in inches. Semi-custom covers like Westland's Select Fit® line use both centerline length and beam to dial in the right size range. Guaranteed-fit covers like Westland's Exact Fit® line are built to your boat's year, make, and model, so the beam is already accounted for in the pattern.
Step 3: Account for Accessories and Add-Ons
Windshields, trolling motors, jack plates, ski pylons, and tower speakers all affect how a ski boat cover with tower fits. If you skip this step, you'll end up with fabric that's too tight, tears at stress points, or doesn't close properly.
Walk around your boat and make a list of everything that sticks up or out. Measure the height of your windshield from the deck to the top edge. Measure how far your trolling motor extends past the bow. Measure the width of your tower or T-top if you have one. These measurements help you choose between a low-profile cover, a tower cover, or a custom-fit option.
For outboard motors, measure from the top of the cowling to the deck. Some covers include a motor hood. Some stop at the transom and leave the motor exposed. If you're storing your boat outside for months at a time, covering the motor prevents UV damage and keeps moisture out of the powerhead.
Westland's Exact Fit® covers are built for specific year, make, and model combinations, so accessories like windshields and rails are already factored into the pattern. If your boat has aftermarket towers or custom add-ons, you'll want a semi-custom cover sized to accommodate them.
When to Choose Semi-Custom vs. Guaranteed-Fit Covers
Semi-custom covers are sized by hull type, centerline length, and beam. They fit a range of boats within a specific size category. Guaranteed-fit covers are built to match a single year, make, and model. Here's when to use each one.
Choose a semi-custom cover if your boat is older than 15 years, if you've made modifications like adding a tower or changing the seating layout, or if your boat is a custom build. Westland's Select Fit® line uses precise sizing ranges to deliver a tight, tailored fit without requiring a factory pattern. You'll measure your centerline length and beam, then choose the size range that matches.
Choose a guaranteed-fit cover if your boat is stock and newer than 1990. Westland's Exact Fit® covers are hand-sewn to match the exact dimensions of your year, make, and model. You don't need to measure anything. You just enter your boat's information, and the cover is built to fit. This is the fastest, most accurate option for boats that haven't been modified.
Both options include Sewn-In Ventilation, which actively prevents mildew by letting moisture escape instead of trapping it under the fabric. That's a feature you won't find in cheaper universal-fit covers, and it's the reason Westland covers don't develop that musty smell after a few months of storage.
Common Measuring Mistakes That Lead to Poor Fit
Most fit problems come from five mistakes: measuring over curves, measuring the trailer instead of the boat, rounding down, forgetting accessories, and using old measurements.
Measuring over curves is the most common error. If you drape your tape measure over the windshield or follow the contour of the deck, you'll get a number that's 6 to 12 inches longer than the actual centerline length. The cover will be too big, and it'll sag in the middle where water pools and fabric stretches.
Measuring the trailer instead of the boat gives you the wrong number. Trailers are longer than boats because of the tongue and sometimes the motor. Always measure the boat itself, from bow to stern, while it's on the trailer or in the water.
Rounding down costs you coverage. If your boat measures 16 feet, 8 inches, you need a 17-foot cover. A 16-foot cover will leave your bow or stern exposed, and that's where UV damage and moisture start.
Forgetting accessories means your cover won't close. If you measure the hull but forget about your 8-inch windshield, the fabric won't fit over it. Measure everything that sticks up, and account for it when you choose your size.
Using old measurements from a previous cover assumes your boat hasn't changed. If you've added a trolling motor, replaced your seats, or installed a new bimini top, measure again. What fit three years ago might not fit now.
Why Fit Precision Matters in 2026
The boat covers market grew from $2.04 billion in 2025 to $2.16 billion in 2026, and most of that growth came from buyers moving away from universal-fit covers toward semi-custom and guaranteed-fit options. Fit precision isn't just about appearance. It's about preventing the kind of damage that destroys resale value.
A cover that's too loose lets wind get underneath and flap the fabric against your gelcoat. That abrasion dulls your hull finish and wears through the marine-grade fabric in high-stress areas. A cover that's too tight tears at the seams when you try to secure it, and it puts stress on your windshield and railings.
Westland has spent nearly 40 years building covers that fit the first time, and the difference shows up in how long they last. Hand-sewn construction and reinforced stress points mean the cover doesn't fail where cheaper options do. Sewn-In Ventilation means your upholstery doesn't grow mildew while the boat sits in storage. And a fit guarantee means you're not guessing whether the fabric will actually cover your bow.
How Westland's Measurement Tools Simplify the Process
Westland's online selector tools let you choose between two paths: enter your year, make, and model for an Exact Fit® cover, or enter your centerline length and beam for a Select Fit® semi-custom cover. Both paths get you to a cover that actually fits.
If you're using the Exact Fit® tool, you don't need a tape measure. You just select your boat from the database, and Westland builds the cover to match the factory specs. If your boat has been modified or isn't in the database, the Select Fit® tool walks you through measuring centerline length and beam, then shows you the size range that fits your dimensions.
Both options are backed by the same guarantee: if the cover doesn't fit, Westland replaces it. That's a level of confidence you don't get from universal-fit covers sold by boat length alone.
What to Do If Your Measurements Fall Between Sizes
If your centerline length is 16 feet, 6 inches, and the size chart offers 16-foot and 17-foot options, go with the 17-foot cover. Extra fabric can be gathered and secured with straps. Missing fabric can't be stretched.
For beam measurements that fall between ranges, choose the wider option. A cover that's slightly wide will still cinch down with tie-down straps and support poles. A cover that's too narrow won't close over your rails, and you'll spend 20 minutes fighting with it every time you try to secure it.
If you're not sure which size to choose, contact Westland's in-house marine canvas experts. They've been sizing covers for nearly 40 years, and they can walk you through the decision based on your specific boat and storage setup.
Frequently Asked Questions
Do I measure my boat with the motor up or down?
Measure with the motor in the position it'll be stored. If you tilt your outboard up for trailering or storage, measure with it tilted. If you leave it down, measure with it down. Most storage covers are designed to fit over a tilted outboard, but you need to know the height from the deck to the top of the cowling to choose the right style.
Can I use my boat's manufacturer specs instead of measuring?
Manufacturer specs give you the hull length, which is usually close to the centerline length but not always exact. If your boat has a swim platform, bowsprit, or extended stern, the manufacturer's listed length won't include those. Measure your boat as it sits today, including any add-ons, to get the most accurate fit.
What if my boat has a custom tower or T-top?
Towers and T-tops require either a semi-custom cover with extra height or a tower-specific cover. Measure the height from the deck to the top of the tower, and measure the width at the widest point. Westland's Select Fit® line can accommodate most tower configurations, and the team can help you choose the right size based on your measurements.
How do I measure a pontoon boat?
Measure the centerline length from the front of the deck to the back of the deck, not including the motor. Measure the beam from the outside edge of one pontoon to the outside edge of the other, including the deck and railings. Pontoon covers are sized differently than V-hull covers because of the wider beam and flat deck, so make sure you're using a pontoon-specific size chart.
Do I need to account for my bimini top?
If your bimini top folds down, measure with it folded. If it's a fixed frame, measure the height and width, and choose a cover designed to fit over it. Some covers include cutouts or extra height for bimini tops. Others are designed to fit under the frame. Know which style you need before you order.
Get the Right Fit the First Time
Measuring your boat for a cover takes 10 minutes and three measurements: centerline length, beam, and accessories. Those numbers determine whether you need a universal-fit cover, a semi-custom Select Fit® cover, or a guaranteed-fit Exact Fit® cover built to your boat's year, make, and model.
Westland has been building hand-sewn, guaranteed-fit boat covers since 1986. Every cover includes Sewn-In Ventilation to prevent mildew, reinforced stress points to prevent tearing, and a fit guarantee that means you're not guessing. If you want a cover that protects your investment instead of just covering it, start with the right measurements and choose a brand that's been trusted by boat manufacturers and serious boat owners for nearly 40 years. Find your guaranteed-fit MasterCraft boat cover with tower at westlandcovers.com.
