Hot Tub Cover Size Guide: How to Measure

Five numbers decide whether a replacement cover seals: length, width, corner radius, skirt depth and fold direction. Take all five, take them twice, and write them down before you go near a checkout. A custom cover is made to your figures, so a wrong figure is a wrong cover with no useful route back.

1. Length and width

Measure the outside of the tub cabinet, at the widest point, not the water surface and not the acrylic rim. The cover has to overhang the shell to seal against the top edge, and every maker sizes from the cabinet for that reason.

Take both measurements at the outer lip, from edge to edge, with the tape flat rather than following any curve. If the two long sides differ by more than a fraction, measure again: tubs are usually square and tape measures usually are not held straight.

2. Corner radius

This is the one people guess, and a guessed radius produces a cover that will not seal along two edges. There is a simple way to get it right without any specialist tool.

1. Lay a large sheet of paper or card over one corner of the tub.
2. Trace the curve of the cabinet corner onto it.
3. Cut along the traced line and check the cut edge sits flush against the corner all the way round.
4. Measure from the point where the curve begins to the imaginary square corner. That distance is the radius.

Common radii cluster around a handful of values, and most makers ask you to pick from a list. If yours falls between two, the cut-card template tells you which side to round to. Do not average them.

3. Skirt depth

The skirt is the flap that hangs down the outside of the cabinet, and it is what stops wind getting under the cover and what completes the seal. Measure how far down the side you want it to hang, typically a few inches.

Too short and the cover sits on top rather than over, and it will lift. Too long and it fouls the cabinet trim or the lifter brackets. If you have a lifter, check its clearance before choosing.

4. Fold direction

Covers fold along a hinge across the middle, and the fold runs either along the length or across the width. That decision determines which side the cover opens toward, which has to match where your lifter is mounted and where you have space.

Stand at the tub and decide which side you want to fold it toward, then specify the hinge running perpendicular to that direction. Getting this wrong is not fatal — the cover still fits — but it means opening it toward a wall for the next several years.

5. Taper and thickness

Not strictly a measurement, but a specification you choose. The taper is the difference in thickness between the middle of the cover and its edges, and it exists so water runs off rather than pooling. A common specification is a taper of about an inch across the panel.

Thicker covers insulate better and weigh more. If a lifter is already fitted, check its rating before ordering the thickest option available, because a heavier cover on a marginal lifter is how brackets bend.

A checklist to take outside

Where to buy, honestly

Genuinely custom-fit covers are sold direct by specialist makers, not on general marketplaces. We are not in any of their affiliate programs, so we earn nothing from pointing you there, and we are pointing you there anyway because a universal cover will not do this job. Get two quotes and compare on foam density, taper and vapor barrier rather than on headline price.

If your cover is not actually finished — if the vinyl is intact and only the foam is heavy — a foam core replacement may be the cheaper answer, and replace or repair works that decision through before you spend on a full cover.

Why the fit matters beyond neatness

Most heat leaves a hot tub as evaporation off the water surface. A cover that does not seal against the rim leaves a gap for that vapor to escape, and the cost shows up on the electricity bill rather than anywhere visible. A cover that seals is also a barrier over water held at spa temperature,^[source] which is a safety consideration as well as an energy one.