421 degrees Celsius = 789.8°F (exact). Rounded: 789.8°F. In Kelvin: 694.15 K. In Rankine: 1249.47°R.
High industrial temperature — used in metalwork, ceramics, and manufacturing.
For context: 0°C = 32°F (freezing), 20°C = 68°F (room temp), 37°C = 98.6°F (body temp), 100°C = 212°F (boiling). The Celsius scale places 0° and 100° at the freezing and boiling points of water at sea level.
All temperature units: 789.8°F · 694.15 K (Kelvin) · 1249.47°R (Rankine). Kelvin starts at absolute zero (−273.15°C). Rankine is used in some US engineering applications.
Formula: °F = (°C × 9/5) + 32. For 421°C: (421 × 1.8) + 32 = 757.8 + 32 = 789.8°F. Reverse: °C = (°F − 32) × 5/9 = (789.8 − 32) × 0.5556 = 421°C.
421°C = 789.8°F (exact: 789.8°F). Formula: (421 × 9/5) + 32 = 789.8°F.
Multiply by 1.8 then add 32: 421 × 1.8 = 757.8, + 32 = 789.8°F. Quick estimate: double the Celsius value and add 30 → 872°F (approximate).
Add 273.15: 421 + 273.15 = 694.15 K. Kelvin is used in science — 0 K is absolute zero (the coldest possible temperature).
High industrial temperature — used in metalwork, ceramics, and manufacturing. In Fahrenheit: 789.8°F is very hot.