Shower Panel Calculator

How Many Shower Panels Do I Need?

The usual answer is the wall area plus 10%, divided by the area of one panel, and it can leave you short. For three walls of 1190mm at 2200mm high that is 3 of the 2.88 m² 2400 × 1200mm panels. The walls actually need 4.

There are two reasons. First, the rule counts every panel as 2.88 m² of wall, but on a 2200mm wall the top 200mm of each panel is cut off, and a Hydrolock panel loses 18mm of width to the joint, so a 1200mm panel covers 1182mm. Each panel gives about 2.60 m² of wall, not 2.88. Second, a wall wider than one finished face needs a start piece and an end piece, so a 1190mm wall takes 2 panels, where the area rule says 1.

So this calculator lays each wall out. Each wall is a start piece, whole panels and an end piece, cut to the trims, and the cutting plan packs every piece from every wall into panels, so the leftover from one wall can finish another. In the table below the area rule is short in 3 of 11 layouts and matches the plan in the others, where the widths happen to divide well. On the walls of 900 + 1500 + 900mm the two agree at 3. Cutting each wall from its own panels only would need 4, which is shown as a second column.

No percentage is added on top, because the plan already reuses leftovers. A spare panel is shown as its own line, like the architrave in the skirting calculator.

How the Layout Works

• Finished face, not panel width. Multipanel: when manufacturing Hydrolock joints, 18mm is lost from the original panel width. A 1200mm panel covers 1182mm, and a 598mm panel covers 580mm.
• Measured between the trims. Multipanel says to allow for the thickness of the aluminium profiles and the space between the walls and profiles, but gives no figure. Enter the visible space each wall's panels fill.
• Cut ends at the trims. Where a panel goes into a trim, the protruding tongued or grooved edge is cut off (Multipanel). No end piece is under 100mm, which is our own choice.
• Groove-side and tongue-side strips. A panel cut across gives a strip that can start a wall and a strip that can end one, and a strip with both edges cut can be a single piece. That is our reading of how the edges fit.
• Leftovers shared between walls. The plan packs the pieces from every wall into panels, with at most one start piece and one end piece in each.

What it does not do: it does not lay walls taller than the panel, cut-outs for valves, base profiles, or square-edge panels, and it does not count adhesive or silicone. Enter the walls as the space between trims.

Panel and Trim Sizes, With Sources

Every panel and trim below has a product page that states its size, and no product page means no dropdown entry. The finished face is the panel width minus 18mm (Multipanel's installation guide, which gives 580mm and 1182mm as examples, so 882mm for the 900mm panel follows from the same rule).

Where the Rules Come From

The fitting rules are from Multipanel's 11mm wall panel installation guide (18mm lost at a Hydrolock joint, the tongued or grooved edge cut off where a panel goes into a trim, silicone at every vertical joint, a 3mm gap above a shower tray as one option, a 2mm clearance round holes, allow for the profile thickness when measuring). The way the pieces are shared between walls, and the 100mm shortest end piece, are our own working. Follow the guide in your pack where it differs, and use the manufacturer's adhesive and sealant to keep the warranty.

Common Layouts: Panels Needed

Generated from the calculator above. Every layout is 2200mm high on 2400 × 1200mm Hydrolock panels with internal corners and an end cap at each end. The "area + 10%" column is the usual rule of thumb, and "area rule short by" is how many panels it would leave you without.

Use the calculator for your own walls. Small changes to a wall width can change the count by a panel. For dry-room slatted panelling, see our slat wall panel calculator.

Frequently Asked Questions

How many shower wall panels do I need?

The usual sum is the wall area plus 10%, divided by the panel area, and it can leave you short. For three walls of 1190mm at 2200mm high it gives 3 of the 2.88 m² 2400 × 1200mm panels, but the walls need 4. There are two reasons. The rule counts every panel as 2.88 m² of wall, but on a 2200mm wall the top 200mm is cut off, and a Hydrolock panel loses 18mm to the joint, so each panel really gives about 2.60 m². And a wall wider than one finished face (1182mm) needs two cut pieces, so a 1190mm wall takes 2 panels, not one. The calculator lays every wall out, so it counts the pieces you actually cut.

How much width does a Hydrolock joint use?

Multipanel's installation guide says that when manufacturing Hydrolock joints, 18mm is lost from the original panel width, and to allow for it when working out how many panels you need. Its examples are a 2400 × 598mm panel giving a 580mm finished face and a 2400 × 1200mm panel giving 1182mm. The calculator uses the finished face, 1182mm for the 1200mm panel, and the same 18mm rule gives 882mm for the 900mm panel.

Where do I measure the wall from?

Measure the space the panels have to fill, between the trims. Multipanel's guide says that when measuring from walls or past shower enclosures, you should allow for the thickness of the aluminium profiles and the space between the walls and the profiles. It does not give a figure to take off, so we do not guess one. Enter the visible width between the profiles, and the visible height, for each wall.

Can I use the leftover from one wall on another?

Often, yes. Where a panel goes into a trim, Multipanel says the protruding tongued or grooved edge should be cut off. A panel cut across gives a groove-side strip, which can start a wall, and a tongue-side strip, which can end one. So one panel can supply the end of one wall and the start of another, and a strip with both edges cut can be a single piece. That last part is our reading of how the edges fit. For the walls above, 2 panels are shared this way, which is how 3 panels do the work of 4.

Which panel width should I choose?

The results rank the 598, 900 and 1200mm Hydrolock panels for your walls by the panel area bought. Any width within 2% of the least area is treated as a tie, and a tie goes to the fewest vertical joints, since every joint is silicone sealed. The table shows the joints for each width, so you can see the trade. A narrow panel can buy a little less area, but at the cost of many more joints.

How many trims do I need?

One at each corner and at each exposed end. Multipanel's Type A internal corner is supplied in 2450mm and 2750mm lengths, and the Type B external corner and Type C end cap in 2450mm. A wall up to 2450mm high takes one length at each position. This calculator counts one length per position, or more if a wall is taller than 2450mm, and shows internal corners, external corners and end caps separately. For the walls above that is 2 internal corners and 2 end caps.

What is the shortest piece I can fit?

Multipanel does not give a minimum. We use 100mm at each end of a wall, which is our own choice, so no piece is a thin strip that is hard to fix and seal. If your wall would leave a narrower gap than that, the calculator balances the two ends or uses one fewer whole panel.

What about sealant and adhesive?

Multipanel says Hydrolock panels must be silicone sealed at every vertical joint, at all extrusions and joints, and at the bottom of the panel, and that its own adhesive and sealant should be used to keep the warranty. The results show how many vertical joints there are, but we do not count cartridges, because we have no coverage figure to base it on. As an alternative to its Seal kit, Multipanel says you can fit a panel with a 3mm gap above a shower tray or bath, sealed with silicone.

Does it work for a wall taller than the panel?

No. The panels are 2400mm high, and a taller wall needs a horizontal join, which this calculator does not lay. It warns you if a wall is higher than the panel. Cut-outs for valves and controls are not modelled either. Multipanel says to leave a 2mm clearance round the edges of any hole, sealed with silicone.

Does it work for square-edge panels?

No, only Hydrolock tongue and groove panels. Square-edge panels use a mid-joint profile instead, and we do not have a sourced figure for how much width that takes.