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Right Ascension to Degrees Converter

Enter right ascension as hours, minutes and seconds to convert to degrees.

Result

101.29°

How it is calculated

The tool turns the three fields into a single number of hours and multiplies by 15: degrees = 15 × (h + m ÷ 60 + s ÷ 3600). Here h is hours, m is minutes of time and s is seconds of time. The factor 15 is 360° divided by 24 hours. Minutes and seconds may be left empty and are then treated as 0; hours are required. Negative values give no result. The engine does not wrap or limit the input, so 25 hours and 75 minutes simply give 393.75°, beyond a full circle. The answer is shown with two decimals and a degree sign.

Worked example

Convert a right ascension of 6 h 45 m 9 s. Minutes as hours: 45 ÷ 60 = 0.75. Seconds as hours: 9 ÷ 3600 = 0.0025. Total: 6 + 0.75 + 0.0025 = 6.7525 h. Multiply by 15: 6.7525 × 15 = 101.2875, displayed as 101.29°. The two-decimal display rounds the value, so keep the unrounded figure if you chain further calculations.

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Common mistakes

  • Treating the minutes and seconds as arcminutes and arcseconds. In right ascension they are minutes and seconds of time, so one minute is 15 arcminutes, not 1.
  • Typing a declination (for example +41° 16′) into these fields. Declination is already in degrees and needs no ×15 conversion.
  • Entering a decimal-hour value in the hours field and then also filling minutes. Put 6.75 in hours with the others empty, or use 6 h 45 m, not both.
  • Typing a negative RA to mean west or before zero. Right ascension runs 0 to 24 h and the tool returns nothing for negative values; add 24 h first.
  • Expecting values over 24 h to wrap back into 0°–360°. The tool does not wrap them.

Sources

About this calculator

Right ascension (RA) is the celestial equivalent of longitude, used in the equatorial coordinate system to locate stars and deep-sky objects. Astronomers traditionally express it in hours, minutes and seconds (since the full 360° circle corresponds to the 24-hour rotation of the sky), which means 1 hour of RA equals exactly 15 degrees (360° ÷ 24h) — the conversion this calculator performs, along with the proportional scaling of minutes and seconds.

Converting RA into decimal degrees is a routine step whenever you need to feed coordinates into telescope-pointing software, plate-solving tools, or any calculation (like angular separation between two objects) that requires both RA and declination expressed in the same degree-based units.

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  • Editorial team

    Two quick checks help here: 6 hours must come out as 90 degrees and 12 hours as 180. Remember that a catalogue RA is tied to an epoch such as J2000, and this conversion only changes units, so it does not shift coordinates to another epoch. Keep the unrounded value if you chain it into later work. Which software or catalogue are the converted numbers going into?

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