Step 1: Measure the rough-in before you do anything else
The single most important measurement when buying a toilet is the rough-in distance — the distance from the finished wall behind the toilet to the center of the closet flange (the bolts that hold the toilet to the floor). In 90% of US homes built after 1970, this is 12 inches. In older homes and certain commercial conversions, it can be 10 inches or 14 inches. The rough-in of your new toilet must match your existing rough-in, or the toilet won't fit and the supply line won't connect properly.
To measure: with the existing toilet still in place, measure from the finished wall to the closet bolts on either side of the toilet base (the silver bolt caps at the bottom). The center of those bolts is the center of the closet flange. If the bolts aren't visible, measure from the wall to the center of where the toilet meets the floor — that's an approximation but works for shopping purposes. Pre-measure twice. A toilet bought with the wrong rough-in is returnable only if the box hasn't been opened.
Step 2: Decide on bowl shape — elongated or round-front
Two bowl shape options: elongated (longer front-to-back, ~30 inches total length, more seating area) and round-front (shorter, ~28 inches total length). Elongated is the more common modern choice and is more ergonomically comfortable for most adult users. Round-front saves about 2 inches of bathroom floor space — meaningful in small bathrooms (under 5'x8') and powder rooms where the toilet projection eats into walking clearance.
Confirm bathroom layout space before choosing elongated. ADA requires 15 inches of clear space on either side of the toilet centerline; building code typically requires 21 inches of clear walking space in front of the toilet. If your bathroom is so tight that an elongated bowl pushes into walking space or sink clearance, round-front is the answer. If you have the space, elongated wins every time on comfort.
Step 3: Choose comfort height vs. standard height
Comfort height (also called "Right Height," "Chair Height," or "ADA Height") toilets have a 17–19 inch floor-to-seat-top dimension. Standard height is 15 inches. The 2-inch difference is meaningful for adults over 5'8", anyone over age 50, and anyone with knee, hip, or back issues. For 90% of US households, comfort height is the default modern pick. The exception is bathrooms used primarily by small children — a 17-inch seat is too tall for a child under 4, who needs their feet to reach the floor for stability.
Step 4: Choose one-piece or two-piece
One-piece toilets fuse the tank and bowl into a single ceramic body — cleaner lines, no gasket leak point between tank and bowl, easier to clean (no joint where mineral grime accumulates), quieter flush. Trade-offs: 30–50% more expensive than two-piece equivalent, heavier shipping weight (90–120 lbs vs. 70–90 lbs), harder to maneuver through tight bathroom doorways during install.
Two-piece toilets have a separate tank that bolts onto the bowl. Less expensive, lighter to handle during install, easier to find at every retailer. The tank-to-bowl gasket is a known leak point at year 8–15, but it's a $15 part and $50 plumber call to swap.
If aesthetics matter and budget allows, one-piece. If budget is the constraint and you don't mind a slightly less polished look, two-piece. There's no flush performance difference — that's determined by the flush mechanism, not the form factor.
Step 5: Choose a flush mechanism
Four main types:
- Gravity-feed (standard) — water from the tank flows by gravity through the flush valve into the bowl. Quietest, simplest, most reliable. Used in 80% of US residential toilets.
- Pressure-assist — a sealed pressure tank inside the porcelain tank compresses air, then releases it to push water at higher velocity. Stronger flush, louder, more complex, used for high-traffic or marginal-plumbing scenarios.
- Vacuum-assist — used in Niagara Stealth models. Pulls air out of the trapway as water flows in, creating suction that clears the bowl with less water. Lets the toilet flush effectively at 0.8 GPF where gravity-feed needs 1.28+.
- Rimless / single-jet — American Standard VorMax, TOTO Tornado Flush, Kohler ContinuousClean. One large angled jet at the back of the rim instead of multiple small rim holes — no scaling buildup, easier to clean inside the rim.
Step 6: Water efficiency — 1.28 GPF or lower
Federal regulation has limited US-sold toilets to 1.6 GPF since 1994, and EPA WaterSense certifies efficient models at 1.28 GPF or less. The current market default is 1.28 GPF. Ultra-low-flow models (0.8–1.0 GPF) save additional water but require careful flush-mechanism engineering to clear bowls reliably; not every 0.8 GPF toilet does the job well. For households on a septic system or in water-stressed regions (California, Arizona, Nevada), the 0.8–1.0 GPF tier is worth the engineering due diligence.
Dual-flush toilets offer two volume options (typically 0.9/1.28 GPF) selected by the user per flush. Real-world water savings are 15–30% vs. single-flush 1.28 GPF, contingent on the household actually using both buttons correctly. Most casual users press the bigger button every time, negating the savings.
Step 7: Pick a brand and model
For most households, the safe brand choices are Kohler, TOTO, and American Standard — all have universal US parts availability, reliable customer service, and engineering that ages well over 15+ years of ownership. For modern designer aesthetics, Duravit and Swiss Madison; for ultra-low-flow water conservation, Niagara; for basement/macerator installations, Saniflo (essentially the only credible US option).
Within each brand, pick the model that matches your use case: Kohler Cimarron for a default comfort-height ADA pick, TOTO Drake for premium build quality at value pricing, American Standard Champion 4 for households where flush power matters most, DeerValley DV-1F0044 for modern aesthetics at mid-tier pricing.