Glossary
Yoseki-ritsu (floor-area ratio)
The legal cap on total floor area relative to lot size, which sets how much building a plot of land can hold.
Yoseki-ritsu is the floor-area ratio: total permitted floor area divided by lot size, expressed as a percentage. A 100-square-meter lot zoned at 200 percent can carry up to 200 square meters of floor area across all stories. This is the number that decides how much you can actually build, and therefore much of what land is worth in dense central wards. It pairs with the building-coverage ratio, which limits footprint. Check both before assuming a site can be redeveloped — an existing building may already max out the ratio, or a non-conforming older structure may exceed today's limit and be impossible to rebuild as-is.