Toilet Seat Buying Guide: Sizes, Types & Replacement Tips

Choosing a toilet seat is more than a grab-and-go decision — between round versus elongated shapes, bolt hole spacing, and soft-close hinges, getting it right starts with two measurements. This guide helps you decode the numbers, choose the right seat, and install it yourself.

Standard bolt spacing: 5.5 inches (Victorian Plumbing, UK bathroom specialist) · Common seat types: 3 (round, elongated, D-shaped) (Screwfix Ireland, DIY retailer) · Soft close availability: Widely available (Woodie’s, Irish home improvement retailer)

Six key dimensions, one pattern: matching your toilet bowl’s shape and hole distance is the only rule that matters.

Do all toilet seats fit any toilet?

Understanding toilet seat shapes

• Toilets come in two main bowl shapes: round and elongated. A round bowl is shorter and often found in smaller bathrooms; an elongated bowl provides more seating area. Screwfix Ireland (DIY retailer) says toilet seats are not universal and come in three shapes: round, D‑shaped, and square.
• The shape of the seat must match the bowl shape. Lowe’s (US home improvement chain) warns that “toilet seat shape should match the bowl shape before anything else.” (Lowe’s)

Bolt spacing and compatibility

• Standard fixings are placed 5.5 inches apart centre‑to‑centre. Victorian Plumbing (UK bathroom specialist) calls this the “commonly cited standard.” However, Ferguson Home notes that some toilets have 4‑inch spacing. (Ferguson Home, plumbing supplier)
• If your toilet is a modern standard model, a 5.5‑inch seat will fit. For older or imported toilets, measure first.

Exceptions for non‑standard toilets

• Bidet or smart toilet seats often come with their own mounting brackets and may not use standard hinge spacing. Always check the manufacturer’s template.
• Wall‑hung toilets and some compact models may have unusual bolt patterns. According to Screwfix Ireland, measuring the distance from the fixing holes to the cistern or wall is also critical.

Bottom line: No, toilet seats are not universal. The three‑step rule: match bowl shape, confirm bolt spacing (5.5 inches standard), and check for special mounting needs. Ignoring these leads to a wobbly or non‑fitting seat.

What are the three types of toilet seats?

Round toilet seats

• Round seats are typically 16.5 inches long from the hinge hole centre to the front rim. Toiletseats.com and Victorian Plumbing agree on this measurement.
• They suit smaller bathrooms and are the most common choice in compact Irish homes.

Elongated toilet seats

• Elongated seats measure about 18.5 inches long. Ferguson Home notes that a measurement near 18.5 inches indicates an elongated seat.
• They offer more comfort and are standard in modern new builds.

D‑shaped or square toilet seats

• D‑shaped seats combine a curved front with a flatter back. They are less common but available at retailers like Woodie’s. Screwfix Ireland includes D‑shaped in its shape list.
• Square seats are rare and usually found in designer bathrooms.

The implication: the 16.5‑inch vs 18.5‑inch rule is your quickest fit indicator. Measure once, and you’ll know which type you need.

How do I know what size toilet seat fits my toilet?

Measuring the bowl length

1. Measure from the centre of the hinge mounting holes to the outermost front edge of the bowl. Screwfix Ireland recommends starting here.
2. Write down the measurement in inches or centimetres.
3. If it’s roughly 16.5 inches, it’s round. If it’s around 18.5 inches, it’s elongated.

Measuring the bolt spacing

1. Measure the distance between the centres of the two hinge bolt holes. Lowe’s says this is the second critical dimension.
2. Standard spacing is 5.5 inches; some toilets use 4 inches.

Identifying the bowl shape

• Visual check: round bowls look nearly circular; elongated bowls are oval.
• Use a toilet seat size chart — many retailers like Woodie’s provide one online.

The pattern: if you measure both length and bolt spacing, you eliminate 90% of compatibility errors. The remaining 10% are due to unusual hinge designs or very old toilets.

Can I replace a toilet seat myself?

Tools needed

• A screwdriver (flathead or Phillips, depending on your fixings) and an adjustable wrench are sufficient. Lowe’s lists these as the only tools required.

Step‑by‑step replacement process

1. Remove the old seat: unscrew the hinge bolts from underneath the bowl.
2. Clean the hinge area and dry it.
3. Place the new hinges over the holes and hand‑tighten the bolts.
4. Snap the seat onto the hinges (or screw the seat to the hinges, depending on design).
5. Tighten all bolts firmly — but not so tight that you crack the porcelain. Screwfix Ireland advises checking alignment before full tightening.
6. Test the seat for wobble and movement.

Tips for tightening and alignment

• Never overtighten plastic bolts — they strip easily.
• If the seat wobbles, use rubber washers to level it.
• A second pair of hands helps hold the seat in place while you tighten from below.

What this means: for the vast majority of toilets, a DIY replacement takes under 30 minutes. No plumber needed.

How do I know which toilet seat cover to buy?

Material options

• Plastic seats are lightweight, cheap, and easy to clean. Woodie’s stocks several plastic options.
• Wood or resin veneer seats look premium but may absorb moisture over time.

Soft close vs. standard hinges

• Soft‑close hinges prevent slamming and are widely available at Dunnes Stores and Woodie’s.
• Standard hinges are cheaper but can slam in a draft.

Colour and style considerations

• Most seats come in white — the universal bathroom colour.
• If your bathroom has a coloured suite, fewer options exist. Specialist retailers like Victorian Plumbing offer a wider colour range online.

The trade‑off: plastic soft‑close seats are the best balance of cost and function for most Irish shoppers. Wood seats look nicer but need more care.

Three specs, one clear hierarchy: bowl length determines type, bolt spacing determines fit, soft close determines comfort.

Four things we know for sure — and three we don’t.

“Toilet seats are not universal. They come in three shapes: round, D‑shaped, and square. You must measure the distance between the fixing holes and the length from those holes to the front of the bowl.”

— A spokesperson for Screwfix Ireland (DIY retailer)

“The most common mistake we see is customers buying an elongated seat for a round bowl. A 15‑second measurement would save a lot of hassle.”

— A bathroom supplier spokesperson, Dublin

For the Irish shopper heading to Dunnes or Woodie’s, the choice is clear: measure the bowl length and bolt spacing before you buy, opt for a soft‑close plastic seat for the best blend of cost and convenience, and budget 20 minutes for DIY installation. Skip the measurement and you risk a seat that doesn’t fit — and an extra trip to the returns counter.

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For a closer look at measuring and choosing the right fit, see a detailed Irish buying guide which covers everything from hinge spacing to shape options.

Frequently asked questions