Of the total area that is used by humans (Agriculture, Urban and Built-up Land),
- urban and built-up land is 1m km²,
- agriculture is 48m km²,
so agriculture is 48 of 49 millions km² used, that’s 98%. The remaining 2% are all streets and housing and other infrastructure together.
I believe It’s close, I worked on a paper about a decade ago, and our numbers were not too dissimilar, actually it’s ridiculous how similar they are. We went with the most extensive data hunt on land usage. We had non-arable land at 14.7%, which rounded up to 15% in our summary. We got multiple sources for global precipitation levels. We got registries from US, Russia, China, India, Brazil, Canada, Australia, etc totalling 65 countries, we extrapolated the rest, our extrapolation was actually 70% of the paper. We back tallied registry numbers with global weather data.