Arcminute (′) - Unit Information & Conversion
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What is a Arcminute?
Arcminute (arcmin or minute of arc) is 1/60 of a degree, measuring small angles in astronomy, surveying, and navigation. Symbol: ′ or arcmin. 1° = 60 arcminutes. Moon and Sun are each about 30 arcminutes in diameter.
History of the Arcminute
Derived from Babylonian sexagesimal (base-60) system used for astronomical measurements. Essential for precise celestial coordinates and navigation since ancient times.
Quick Answer
What is an Arcminute? An arcminute is 1/60 of a degree, used for measuring small angles. The Moon appears about 30 arcminutes wide in the sky. 1 arcminute = 60 arcseconds = 1/60 degree ≈ 0.0167°. Use our angle converter for instant conversions.
Key Facts: Arcminute
| Property | Value |
|---|---|
| Symbol | ' |
| Quantity | Angle |
| System | Metric/SI Derived |
| Derived from | Radian |
| Category | Angle |
| Standard Body | NIST / ISO |
Definition
1 arcminute = 1/60 degree = 60 arcseconds ≈ 0.0167° ≈ 0.000291 radians
Symbol: ′ (prime) or arcmin
Common Uses
Astronomy: Measuring apparent sizes of celestial objects and their positions. Surveying: Land measurement and mapping precision. Navigation: GPS coordinates (latitude/longitude precision). Ophthalmology: Visual acuity testing (20/20 vision = 1 arcminute resolution).
Real-World Examples
Celestial Objects (Apparent Size)
How large things appear in the night sky:
| Object | Apparent Diameter | In Arcminutes | Notes |
|---|---|---|---|
| Sun | 0.53° | 31.8' | Perfect match for Moon at totality |
| Full Moon | 0.52° | 31.2' | Slightly smaller than Sun |
| Jupiter | 30-50″ | 0.5-0.83' | Depends on distance |
| Venus | 10-65″ | 0.17-1.08' | Highly variable |
| Mars | 4-25″ | 0.07-0.42' | Farthest and nearest approach |
| Saturn | 16-21″ | 0.27-0.35' | Major axis of rings |
| Sirius (bright star) | ~0.005″ | ~0.0001' | Tiny point even in telescopes |
| Andromeda Galaxy | 3° × 1° | 180' × 60' | Extends much larger |
Reference: Moon and Sun nearly identical in size - why total solar eclipses occur
Navigation and Geography Applications
Latitude and longitude precision:
| Precision | In Degrees | In Arcminutes | Distance at Equator | Use Case |
|---|---|---|---|---|
| 1 degree | 1° | 60' | 111 km | Regional (city-level) |
| 1 arcminute | 0.0167° | 1' | 1.85 km (1 NM) | GPS basic precision |
| 1 arcsecond | 0.000278° | 1" | 30.9 meters | Surveying precision |
| 0.1 arcsecond | 0.0000278° | 0.1" | 3 meters | High-precision GPS |
| 1 milliarcsecond | 0.0000003° | 0.001" | 3 cm | Geodesy/research |
Rule: 1 arcminute latitude = 1 nautical mile (used in maritime navigation)
Vision and Optical Resolution
Human visual acuity benchmarks:
| Condition | Resolution | In Arcminutes | Ability |
|---|---|---|---|
| Exceptional vision | 20/10 | 0.5' | Can read 20/10 letter at 20 feet |
| Perfect (20/20) | 20/20 | 1' | Standard "normal" vision |
| Good | 20/30 | 1.5' | Can read 20/30 letter at 20 feet |
| Needs correction | 20/40 | 2' | Sees at 20 feet what normal sees at 40 |
| Poor | 20/70 | 3.5' | Significantly impaired |
| Very poor | 20/100 | 5' | Nearly legally blind |
| Legally blind | 20/200 | 10' | Threshold of legal blindness |
| Severe | 20/400 | 20' | Minimal light perception |
Telescope limit: Best telescopes resolve ~0.1 arcseconds (not seeing point)
Surveying and Mapping Accuracy
Land survey precision requirements:
| Survey Type | Typical Accuracy | In Arcminutes | Application |
|---|---|---|---|
| Rough survey | ±100 meters | ±0.05' | Approximate boundaries |
| Standard survey | ±30 meters | ±0.015' | Property boundaries |
| Precision survey | ±5 meters | ±0.003' | Engineering layouts |
| High-precision | ±1 meter | ±0.0006' | Major construction |
| Geodetic survey | ±10 cm | ±0.00006' | Control points |
| GPS mapping | ±5-10 meters | ±0.003-0.006' | General mapping |
| RTK-GPS | ±2-5 cm | ±0.00001-0.00002' | Precision construction |
Angular Size Comparison
How different angles appear visually:
| Angular Size | Visual Appearance | Real Examples |
|---|---|---|
| 1 arcminute | Barely visible detail | Reading letter at 20 feet (20/20 vision) |
| 5 arcminutes | Small object | Letter height in standard print at arm's length |
| 15 arcminutes | Obvious object | Thumb width at arm's length |
| 30 arcminutes | Large object | Moon in the sky, half-degree angle |
| 1 degree | Easy to see | Sun in the sky, full moon |
| 5 degrees | Obvious | Hand width at arm's length (all fingers) |
| 10 degrees | Very obvious | Fist at arm's length |
| 90 degrees | Right angle | Edge of room to corner |
Arcminute Conversion Formulas
To Degree:
To Radian:
To Gradian:
To Arcsecond:
To Turn:
To Revolution:
To Quadrant:
To Gon:
To Mil:
Frequently Asked Questions
Formula: Degrees = Arcminutes ÷ 60 Examples:
- 60 arcminutes = 1°
- 30 arcminutes = 0.5° (Moon's diameter)
- 120 arcminutes = 2° Arcminutes to Degrees converter →
Convert Arcminute
Need to convert Arcminute to other angle units? Use our conversion tool.