According to Paolo Ardoino, Tether’s USDT supply stands at 173B as of Sep 23, 2025, based on his public post stating 173B USDT, source: Paolo Ardoino on X, Sep 23, 2025. USDT is designed to track 1 USD per token, so 173B USDT implies roughly 173 billion dollars of dollar-pegged stablecoin float available to crypto markets, source: Tether website About Tether and FAQs. Growth in circulating stablecoin supply has been associated with deeper order books and tighter spreads for BTC and ETH, improving execution conditions for traders, source: Kaiko Research report on stablecoins and market liquidity 2024. Institutional market commentary has also documented a positive relationship between stablecoin market cap changes and overall crypto liquidity and activity, making USDT supply a key metric for gauging risk appetite, source: Coinbase Institutional Market Commentary 2024.