21 degrees to radians
0.3665 rad
21° = 0.3665 rad.
radians
0.3665rad
21° = 0.3665 rad
In short
How many radians is 21 degrees?
21° = 0.3665 rad. 1 degree = 0.017453 radians, so the working is 21 × 0.017453 = 0.3665.
The working
The factor below is an exact definition rather than a measurement, so nothing is approximated in the arithmetic. The only rounding on this page happens where a number is displayed.
1 degree = 0.017453 radians 21 × 0.017453 = 0.3665
How much precision do you need?
Each row is the same answer cut at a different number of decimals, with what that choice costs you. Pick the shortest row whose error is smaller than whatever you are measuring with.
| Rounded to | Answer (rad) | Off by |
|---|---|---|
| Whole number | 0 | −0.36652 |
| 1 decimal | 0.4 | +0.03348 |
| 2 decimals | 0.37 | +0.00348 |
Round trip: take 0.3665 rad back the other way and you land on 20.9989° — a drift of 0.0011°. That gap is the rounding, not the conversion.
Frequently asked questions
What is 21 degrees in radians?
21 degrees is 0.3665 radians. 1 degree = 0.017453 radians, so the working is 21 × 0.017453 = 0.3665.
How accurate is 0.3665 rad?
Rounding to 0.3665 rad and converting straight back gives 20.9989°, a drift of 0.0011° from the 21 you started with. The factor itself is exact; every bit of that difference comes from the rounding, not the conversion.
Nearby values
Any value at all
Degrees to Radians Converter
Convert degrees to radians — trigonometry, calculus, and anything using π.
Open the degrees to radians converter →