The most important measurement you need when shopping for a new bathroom faucet is the spacing between the holes on the sink or countertop. This isn't a challenging measurement to make, because there are only three possibilities. If you're installing a new vanity, you'll also need the width of the countertop and the distance between the faucet holes and the backsplash. Don't forget the distances between the faucet connections and the supply valves -- this is crucial information when shopping for flexible supply hoses.
Standard Hole Spacing
You'll see two or three holes on your sink or countertop, and the relevant measurement is the spacing between the centers of the outer holes. You can often identify the spacing just by looking, but if not stretch a tape measure between them:
- 4 inches is the standard spacing for the compact centerset faucets, a single-piece faucet needing either three holes, for the hot and cold water valves and the drain popup, or two holes with no popup.
- 4, 6 or 8 inches are the standard spacings for mini-widespread bathroom faucets, which consist of three separate pieces. All are three-hole configurations, allowing for the valves and the spout.
- From 8 to 16 inches are the available spacing for bathroom widespread faucets, with three separate holes that you can install at intermediate and near-random widths if you see fit.
- The less-common wall mount faucets, useful for contemporary design or when there is no space for a faucet in the sink, come in similar configurations to deck-mounted centerset and widespread faucets.
Make Sure There's Room
If you're modifying the backsplash as part of the faucet replacement project, you'll need another measurement -- the distance from the centers of the holes to the backsplash. Compare this measurement to the width of the faucet base to be sure the faucet will fit before buying it.
If you're renovating the vanity, you may not be legally bound to make it accessible to people with disabilities under the Americans with Disabilities Act, but doing so prevents future liability issues. To make the vanity ADA compliant, the top of the vanity must be no more than 34 inches above the floor, and the maximum reach from the front of the vanity to the faucet cannot exceed 20 inches. Moreover, you cannot require people to reach higher than 44 inches to access the faucet. Keep these numbers in mind when constructing the vanity and measuring for your faucets -- especially wall-mounted ones.
Flexible Hose Length
After you've installed the faucet, you need flexible hoses to connect it to the water supply, and these come in a variety of lengths. Prevent repeated trips to the hardware store by measuring the distance from each faucet connector to its corresponding shut-off valve, then add about 2 or 3 inches and purchase the hose with the length closest to that measurement. Just as you don't want to buy a hose that's too short, you don't want one so long that it curls around under the sink claiming valuable shelf space.