Multiply by 9, divide by 5, then add 32: (°C × 9/5) + 32 = °F. Example: 25 °C = 77 °F (25 × 1.8 + 32). Quick mental shortcut: double the Celsius, subtract 10 %, add 32. Example: 20 °C → 40 − 4 + 32 = 68 °F (exact). The tool gives the precise result instantly — no mental arithmetic required.

Subtract 32, multiply by 5, then divide by 9: (°F − 32) × 5/9 = °C. Example: 98.6 °F = 37 °C exactly. Shortcut: subtract 32, then divide by 1.8. Example: 68 °F → 36 ÷ 1.8 = 20 °C. The formula works for all values including negatives — enter −40 °F and you get −40 °C, the one point where both scales intersect.

Add 273.15: °C + 273.15 = K. Example: 0 °C = 273.15 K; 100 °C = 373.15 K. Kelvin matters because it is the SI base unit of thermodynamic temperature — equations in physics and chemistry (gas laws, radiation laws, entropy) require an absolute scale with no negative values. A temperature of 0 K (absolute zero, −273.15 °C) is the point where molecular motion theoretically ceases entirely.

Yes — 37 °C = 98.6 °F exactly by the formula (37 × 9/5 + 32). The difference is purely the scale used. 37 °C is the clinical standard in most countries; 98.6 °F is its US equivalent. In practice, normal body temperature ranges from roughly 36.1–37.2 °C (97–99 °F) depending on time of day, measurement site (oral, rectal, axillary), age, and activity level.

0 °C = 32 °F — the freezing point of pure water at sea level. 100 °C = 212 °F — the boiling point of pure water at 1 atm. These are the two defining anchors of the Celsius scale. The 180 °F range between freeze and boil equals exactly 100 °C, meaning 1 °C = 1.8 °F in terms of interval size. Kelvin equivalents: 0 °C = 273.15 K, 100 °C = 373.15 K.

The same formula applies: (°C × 9/5) + 32 = °F. Negative Celsius values produce Fahrenheit values that may still be positive, zero, or negative. Examples: −10 °C = 14 °F; −17.78 °C ≈ 0 °F; −40 °C = −40 °F. The crossover at −40 is the only point where °C and °F are numerically equal. Below −40 °C, Fahrenheit values are less negative than Celsius values.

Kelvin shares the same degree interval size as Celsius — a 1 K change equals a 1 °C change. The difference is the zero point: Celsius anchors at water's freezing point, while Kelvin anchors at absolute zero (0 K = −273.15 °C), the lowest theoretically possible temperature. Fahrenheit uses a larger interval (1 °F ≈ 0.556 °C) and its own historical zero. There is no "degree" symbol for Kelvin — it's written as K, not °K.

Rankine (°R) is an absolute scale using Fahrenheit-sized steps. 0 °R = absolute zero; 491.67 °R = water's freezing point. It's used in US aerospace and thermodynamics where engineers prefer Fahrenheit-based absolute temperature. Réaumur (°Ré) runs 0–80 between water's freeze and boil points. It's largely historical but still referenced in European cheesemaking (Gruyère aging, for instance). Formula: °C × 4/5 = °Ré.

Three steps: (1) Type any temperature value — integers and decimals work (e.g., 36.6 °C, −10 °F, 300 K, 25.5 °Ré). (2) Select the source scale from the dropdown: °C, °F, K, °R, °Ré, or °De. (3) All other scales update instantly in the output panel. Tap the Copy button next to any result to copy it directly to your clipboard. No login, free at untangletools.com/unit/category/temperature.

Yes — decimal inputs are fully supported. Examples: 36.6 °C → 97.88 °F (common thermometer reading); 98.2 °F → 36.78 °C; −17.5 °C → 0.5 °F. The tool uses 64-bit floating-point precision, so results are accurate to many decimal places. Fractions are equally valid — enter 98 ½ as 98.5 and the conversion is exact.

Yes — all of them plus Delisle. Full scale support: Celsius (°C), Fahrenheit (°F), Kelvin (K), Rankine (°R), Réaumur (°Ré), Delisle (°De). Each scale is selectable as the source input, and all others output simultaneously. Delisle is an inverted scale (higher numbers = colder), which the converter handles correctly — entering 0 °De returns 100 °C = 212 °F = 373.15 K.

Yes. All formulas use exact internationally recognised conversion constants: 273.15 (°C ↔ K offset), 9/5 ratio (°C ↔ °F interval), 459.67 (°F ↔ °R offset). Results are computed with full 64-bit floating-point precision — no rounding at intermediate steps. Completely free at untangletools.com/unit/category/temperature with no account required.

Absolute zero is 0 K = −273.15 °C = −459.67 °F. It represents the theoretical minimum of thermodynamic temperature — the state at which a system's particles have minimum possible kinetic energy. The third law of thermodynamics states that absolute zero can be approached but never fully reached in practice. The coldest temperatures ever achieved in laboratories are within billionths of a Kelvin above absolute zero, achieved through laser cooling and adiabatic demagnetisation.

The scales intersect at exactly −40 — that is, −40 °C = −40 °F. This is the only point where both readings are numerically identical. You can verify it: −40 × 9/5 + 32 = −72 + 32 = −40. Above −40, the Fahrenheit value is always higher than Celsius; below −40, Fahrenheit values become less negative than Celsius (e.g., −50 °C = −58 °F, not −50 °F).

Use the standard formula (°C × 9/5) + 32 = °F or common cooking benchmarks: 150 °C = 302 °F (slow/warm); 180 °C = 356 °F (moderate baking); 200 °C = 392 °F (hot); 220 °C = 428 °F (very hot). Gas Mark 4 ≈ 180 °C ≈ 356 °F. Fan-forced ovens typically run 15–20 °C hotter than stated, so subtract before converting.

Normal body temperature is approximately 37 °C / 98.6 °F. A fever begins around 38 °C / 100.4 °F. A high fever is 39–40 °C (102.2–104 °F). Above 40 °C / 104 °F is considered severe and warrants immediate medical attention; above 41.5 °C (106.7 °F), hyperthermia can cause organ damage. These thresholds apply to oral measurements — rectal readings run ~0.3–0.5 °C higher.

Fahrenheit was the dominant scientific standard in the 18th century when the US adopted its measurement conventions. Celsius gained international adoption through the metric system formalised in the 19th–20th centuries. The US retained Fahrenheit in everyday use even as the scientific community globally shifted to Celsius and Kelvin. Today, only the US, the Cayman Islands, and a few other territories use Fahrenheit officially — the rest of the world uses Celsius for weather and daily life.

Created in 1732 by Joseph-Nicolas Delisle, who calibrated his mercury thermometer starting from the boiling point of water as 0 °De and counting upward as temperature decreased. Higher Delisle numbers = colder temperatures — the inverse of every other common scale. Formula: °De = (100 − °C) × 3/2. Absolute zero is 559.725 °De. The scale was used in Russia until the mid-1700s and appears frequently in historical scientific literature.

Temperature is an intensive property — a measure of the average kinetic energy per particle in a substance, independent of amount. Heat is energy in transit, measured in joules or calories, and depends on the quantity of matter. Kelvin is essential for heat calculations because formulas like the Stefan–Boltzmann law (P = σT⁴) require absolute temperature — inserting a negative Celsius value would produce a physically meaningless result.

Liquid nitrogen boils at −195.79 °C / −320.42 °F / 77.36 K at atmospheric pressure. When exposed to room temperature (~22 °C), it instantly absorbs enough heat to vaporise — the 218 °C difference drives rapid phase transition. This makes it effective for rapid freeze-drying, cryogenic storage of biological samples, and superconductor cooling. The visible "smoke" is condensed water vapour from surrounding air, not nitrogen gas itself.