The V scale (named after John "Vermin" Sherman, who developed it at Hueco Tanks, Texas in the 1990s) is the dominant bouldering grade system used across the United States, the UK, and most non-French-speaking parts of the world. It runs from "VB" (V Beginner — easiest) and "V0" (V Easy) up to V17, which is currently the highest confirmed grade in the world.
The scale is open-ended: V18 and harder remain theoretically possible. Each grade is roughly equivalent in difficulty to the next, though the gap between grades widens at the top — a V14 is far harder than a V13 in absolute terms, even though numerically they're adjacent. Grades are determined by community consensus, not by an objective measure, so a V5 at one gym may feel like V4 or V6 at another.
The V scale exists alongside the French Font scale (used in France and parts of continental Europe). Rough conversions: V0 ≈ 4, V3 ≈ 6A, V6 ≈ 7A, V10 ≈ 7C+, V14 ≈ 8B+, V17 ≈ 9A. Beginners typically start at VB or V0, progress to V2–V3 in their first months, and slow to a 6-month-per-grade pace once they hit V4–V5.