How to Pick the Perfect Fit for Your Waterproof Cast Cover

Getting the sizing right on your waterproof cast cover makes a real difference to how well it protects you day to day. A cover that’s too snug can be a real struggle to pull on, while one that’s too loose won’t create the watertight seal you’re relying on. Neither works well when all you want is to shower in peace or get back in the pool.

We manufacture a full range of waterproof cast covers for adults and children, arms and legs, plus dedicated foot covers for more specific injuries. Below, we outline exactly what to measure and how to choose the correct size with confidence.

Why the Right Size Matters

Getting your sizing spot on isn’t just a nice-to-have; it genuinely changes how well the product performs. Here’s what you gain when you measure correctly:

• A tighter, more reliable waterproof seal
• Better comfort while you’re wearing it
• A cover that’s easier to put on and take off
• Far less chance of any leaks getting through
• More confidence showering, bathing or heading for a swim

In short, the right fit takes the guesswork out of your daily routine and lets you get on with recovering.

What Should You Measure?

Two measurements matter here: length and circumference. Both play a part in how your waterproof cast protector performs, so it pays to take a few minutes and do this properly rather than eyeballing it. Once you have both figures, you can check them straight against our Size Guide to confirm which model suits your cast.

Measure the Length

For arm covers, measure from your fingertips all the way to about 5cm above where your cast ends. For leg covers, start at your heel and measure up to roughly 5cm above the top of the cast.

That extra 5cm isn’t just padding for good measure. It gives the cover enough length to seal against healthy skin above the cast, rather than trying (and failing) to seal against the cast itself, which leaves water sneaking through.

Measure the Circumference

Next, measure around the thickest part of your cast, since this is what determines how the cover stretches to fit. A soft tape measure works best here. If you don’t have one lying around the house, a piece of string wrapped around the cast and then measured against a ruler does the job just as well.

Choosing the Right Cover for Your Injury

Once you’ve got your measurements, matching them to the right model is fairly straightforward.

Wrist and Lower Arm Casts

If your cast sits below the elbow, a standard arm cover sized to your length and circumference measurements will suit you well. Check our Adult Arm Covers for the full-size range.

Casts That Include the Elbow

Casts extending past the elbow need a longer arm model, so the seal lands on unaffected skin further up rather than stopping short.

Lower Leg Casts

For casts below the knee, a standard leg cover will do the trick, provided your length and circumference measurements line up with the size chart.

Above-the-Knee Casts

If your cast runs above the knee, you’ll want a longer leg option, giving the extra reach needed to seal above the cast rather than fighting against it.

Foot and Toe Injuries

For foot or toe injuries, there’s a dedicated foot cover built specifically for this purpose. In some cases, particularly where the cast sits a bit higher, the smallest leg models might actually suit better, so it’s worth checking both against your measurements.

Choosing Between Adult and Child Sizes

Child sizes are built with smaller proportions in mind and suit younger kids well. Once a child is approaching their teenage years, though, or is already a similar size to an adult, the child range may run out of room to seal properly.

This is where measurements should take priority over age. A twelve-year-old who’s already tall for their age might genuinely need an adult-sized cover, while a smaller teenager might still be comfortably within the child range. Don’t assume; measure and compare against both size charts.

Common Sizing Mistakes to Avoid

A few slip-ups come up again and again, so here’s what to watch for:

• Measuring your limb rather than the cast itself
• Forgetting to add the extra 5cm for the seal
• Skipping the circumference measurement altogether
• Choosing purely based on age instead of actual size
• Guessing rather than measuring properly

Any one of these can leave you with a cover that doesn’t seal properly, so it’s worth the extra few minutes to get it right the first time.

How Should a Waterproof Cast Cover Fit?

A properly fitted cover should form a snug seal against your skin without restricting circulation or feeling like it’s cutting off blood flow. It should slide over your cast without you having to wrestle it into place or stretch it beyond its limits, and it should stay put through a full shower or swim session.

If at any point it feels excessively tight, or you notice numbness, tingling, or discolouration, take it off straight away. Comfort and circulation always come first.

What If You’re Between Sizes?

It happens more often than you’d think, and it’s not something to stress over. Check whether it’s the length or the circumference that’s borderline, since a slightly longer measurement usually points you towards the larger size (a touch of extra length still seals well, whereas a cover that’s too short won’t reach past the cast). If you’re still unsure, contact us directly before ordering, and our team will help confirm the best fit.

FAQs

Does the cover work with both plaster and fibreglass casts? 

Yes, sizing works the same way regardless of cast material, since it’s based on your measurements rather than what the cast is made from.

Can I reuse my cast cover? 

Absolutely, these are designed to be used again and again throughout your recovery, not thrown away after one use.

How long will it last? 

With reasonable care, a cover will comfortably see you through your entire rehab period.

Will it cut off blood flow if worn for too long? 

A correctly sized cover shouldn’t restrict circulation, provided it isn’t sized too small to begin with. That said, covers are meant for showering, bathing, and swimming rather than all-day wear, so remove it once you’re done and let your skin breathe.

Can I use the same waterproof cast cover for a cast and a moon boot? 

It depends on the measurements. A cover sized for a cast may not seal properly over a moon boot’s bulkier shape, so measure the boot separately and check it against our size guide rather than assuming one cover will fit both.

Will ACC cover the cost? 

If your injury is ACC-registered, your cover may be claimable. Check our ACC Orders page for the details.

Getting the Fit Right

A correctly sized cover only takes a few minutes to sort out, and it’s time well spent given how much easier it makes your daily routine. If you’d like a hand confirming your numbers, our Fitting Instructions page walks through the process, or contact us directly.