When will Vietnam overtake Japan in population?

This crossover is driven mainly by Japan's decline. Vietnam's fertility is already below replacement at 1.9 births per woman, and the UN projects its population to peak around 2050, only a few years after it passes Japan. Japan, with 1.2 births per woman and a median age of 49, falls faster. Both countries are projected to be smaller in 2100 than they are today.

Vietnam is projected to overtake Japan in total population around 2045. At the crossover, both countries sit at roughly 109 million people. Today Japan is still larger, but the trend lines are converging and the order is set to flip within a generation.

The reason is a tale of two trajectories. Vietnam is projected to shrink over the century, moving from about 101 million in 2024 toward 92.0 million by 2100. Japan, by contrast, is projected to fall sharply, going from roughly 124 million to 77.0 million over the same period. Differences in fertility and age structure (Vietnam's median age near 33 versus Japan's near 49 today) explain much of the divergence.

Crossovers like this one are how the global population ranking is quietly rewritten. As faster-growing populations climb the table and slower-growing or shrinking ones slip down, the list of the world's largest countries in 2100 will look markedly different from today's. The 2045 crossing is one of the clearer signals of that shift.

As with all long-range projections, the exact year carries uncertainty. Under the UN's high and low fertility scenarios the crossover could arrive earlier or later, and the figures here follow the medium variant. Still, the direction of travel, Vietnam rising relative to Japan, is robust across the plausible range of outcomes.