“The pizza has a 12-inch radius.”
Usage Entry 1327 / 1350 60-second read
Diameter vs. Radius
The distance across a circle through the centre versus from centre to edge.
The comparisoni
“The pizza has a 12-inch diameter (6-inch radius) — diameter is the full distance across.”
The ruleii
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DIAMETER = 2 × RADIUS.
DIAMETER is the distance across a circle through its centre — edge to edge. RADIUS is half the diameter — centre to edge. Pizza sizes are given in diameter. Area = π × r². Don't mix them up or you'll get a pizza 4× the size you wanted.
Memory aidiii
Remember it like this
Diameter is the full line.