For a deck-mounted bathroom faucet, compare the outlet's reach with the actual basin edge rather than choosing by faucet height alone. Moen's method subtracts the mounting lip and half the hole diameter from the faucet's center-to-center dimension. Use the exact faucet version and sink drawing; that geometry helps plan fit but cannot guarantee splash-free operation.
Distinguish height from horizontal reach
This question concerns a faucet mounted through the sink or countertop deck. Its spout can clear the rim yet still discharge too close to the back of the basin. Compare the faucet and sink drawings before ordering rather than treating a matching hole count as the complete fit check.
Moen describes lavatory reach as the distance the outlet overhangs from the back of the sink. Too little space can put hands against the rear of the bowl or contribute to splashing. A tall faucet does not necessarily extend farther over the basin.
Choosing a bathroom sink covers the wider mounting and drain checklist. Here the decision is where the outlet will sit relative to the actual bowl opening.
Use the same measurement reference points
Moen's guide uses three dimensions: C is the center of the faucet body to the center of its aerator, L is the mounting lip area between the sink edge and mounting hole, and D is that hole's diameter. Its calculation is R = C - (L + D/2).
Measure or obtain the specified dimensions using the guide's diagram. Do not mix a finished-wall dimension with a deck-hole center, or substitute the overall spout length for C. A different sink's mounting lip can change the resulting reach even with the same faucet.
Check the actual product version
The cited Moen Weymouth S42107 specification warns that the model has more than one version and directs readers to identify theirs. It provides model-specific dimensional drawings. Its figures are examples for that product, not minimum dimensions for every bathroom faucet.
Ask for the correct specification sheet and the chosen sink's drawing. Include backsplash and handle movement clearance, mounting thickness and the bowl's actual location. A drawing for an older faucet version or a different sink can leave the comparison wrong.
Do not turn the calculation into a splash guarantee
Reach describes placement; it does not model every water stream, hand position or basin shape. Confirm the faucet's intended installation and flow characteristics with the sink and faucet suppliers. Low-flow faucet operation is another part of the selection, not proof of compatible geometry.
For an existing installation, record where water lands and whether splashing changed after a part or faucet replacement. Do not bend the spout or install an unapproved outlet attachment to compensate. The broader faucet replacement guide explains connection precautions; it does not replace the bathroom model's fit instructions.