The Science category covers three angular and physical science measurement areas: angle (for geometry, navigation, and engineering), frequency (for electronics, RF, and signal processing), and density (for materials science, chemistry, and fluid mechanics).

Angle: degrees to radians and beyond

The degree (°) is the everyday unit — learned in school geometry, used in compass bearings, protractors, and specifying slopes and inclinations. The radian is the SI standard and is required for all trigonometric functions in mathematics and programming. The relationship: 2π radians = 360 degrees, so π radians = 180° and 1 radian ≈ 57.296°.

The Angle Converter also covers the gradian (used in European surveying), arc minutes and arc seconds (for GPS coordinates and astronomy), milliradians (used in military ballistics and scope adjustments), and turns (useful in rotational mechanics). For students, the most frequent use is converting angle inputs before calling Math.sin() or Math.cos() in Python, JavaScript, or C++, all of which expect radians.

Frequency: from sound to light

The hertz (Hz) is the SI unit of frequency — one cycle per second. Human hearing spans 20 Hz to 20,000 Hz (20 kHz). Radio frequencies span kHz to GHz. Processor clock speeds are in GHz. Optical light frequencies are in THz. All of these are the same quantity — cycles per second — just at vastly different scales.

The Frequency Converter covers the full practical range from Hz through THz, plus RPM and RPS for rotational applications. It is useful for comparing radio frequency band allocations, processor performance specifications, motor speeds, and signal processing parameters.

Density: materials and fluids

Density (mass per unit volume) is a fundamental property used to identify materials, calculate weights from volumes, and assess buoyancy. The SI unit is kg/m³, but laboratory and chemical work often uses g/cm³ (= g/mL), and American engineering uses lb/ft³ or lb/gallon.

The Density Converter is useful for materials engineers comparing datasheets that mix SI and imperial units, chemists calculating solution concentrations, and anyone working with fluid systems where density is needed for flow calculations or buoyancy analysis.

Frequently Asked Questions

What converters are in the Science category?

The Science category includes the [Angle Converter](/angle-converter/) (degrees, radians, gradians, arc minutes, arc seconds, turns, milliradians), the [Frequency Converter](/frequency-converter/) (hertz, kilohertz, megahertz, gigahertz, terahertz, RPM, RPS), and the [Density Converter](/density-converter/) (kg/m³, g/cm³, g/L, lb/ft³, lb/gallon). These converters serve physics, engineering, electronics, and materials science applications.

How do I convert degrees to radians?

Multiply degrees by π/180 (approximately 0.017453). For example, 90° × π/180 = π/2 radians ≈ 1.5708 rad. Key values to know: 180° = π rad, 360° = 2π rad, 45° = π/4 rad, 30° = π/6 rad. Radians are the SI unit for angles and are required for most mathematical functions in programming languages (Math.sin(), Math.cos() in JavaScript, Python, etc. all take radians). The [Angle Converter](/angle-converter/) handles the conversion precisely and also covers gradians and arc minutes/seconds.

What is a gradian and where is it used?

A gradian (also called gon or grade) divides a full circle into 400 units, so a right angle = 100 gradians. Gradians were designed to make calculations involving right angles simpler in survey work and land measurement. They are used primarily in European surveying, civil engineering, and some military applications. 1 gradian = 0.9 degrees = π/200 radians. The [Angle Converter](/angle-converter/) converts between degrees, radians, gradians, and other angular units.

What is the difference between RPM and Hz for frequency?

RPM (revolutions per minute) and Hz (hertz, cycles per second) both describe periodic events but use different time bases. 1 Hz = 60 RPM (one cycle per second = sixty cycles per minute). A car engine idling at 700 RPM runs at 11.67 Hz. A hard disk drive spinning at 7,200 RPM rotates at 120 Hz. The [Frequency Converter](/frequency-converter/) converts between RPM, RPS (revolutions per second), and the SI Hz scale from Hz through terahertz (THz).

What frequencies correspond to common radio bands?

AM radio in India: 531–1,602 kHz (medium wave). FM radio in India: 88–108 MHz. 4G LTE bands: 700 MHz, 1800 MHz, 2100 MHz, 2300 MHz. 5G bands: 700 MHz, 3.3–3.6 GHz, 26 GHz (mmWave). Wi-Fi: 2.4 GHz or 5 GHz bands. Visible light: 430–770 THz. The [Frequency Converter](/frequency-converter/) converts between Hz, kHz, MHz, GHz, and THz — spanning the entire electromagnetic spectrum from audio frequencies to near-visible light.

What is the density of water and common materials?

Water at 4°C = 1,000 kg/m³ = 1 g/cm³ = 1 g/mL = 1 kg/L. This is the standard reference density. Aluminium ≈ 2,700 kg/m³; steel ≈ 7,850 kg/m³; gold ≈ 19,300 kg/m³; air at sea level ≈ 1.225 kg/m³; balsa wood ≈ 120 kg/m³. Any material with density less than 1,000 kg/m³ floats in water. The [Density Converter](/density-converter/) converts between kg/m³, g/cm³, g/L, lb/ft³, lb/US gallon, and lb/UK gallon.

What is arc second and arc minute used for?

Arc minutes (') and arc seconds (") are subdivisions of degrees for very precise angular measurements. 1 degree = 60 arc minutes = 3,600 arc seconds. They are used in astronomy (star coordinates, telescope pointing), GPS accuracy specifications (GPS accuracy ~10 metres ≈ 0.0001 degrees ≈ 0.3 arc seconds), navigation (latitude/longitude in degrees-minutes-seconds format), and optometry (visual acuity, where 1 arc minute is the reference for 20/20 vision). The [Angle Converter](/angle-converter/) converts all these units.

How do I convert g/cm³ to kg/m³?

Multiply g/cm³ by 1,000 to get kg/m³. For example, 2.7 g/cm³ (aluminium) = 2,700 kg/m³. This relationship exists because 1 cm³ = 10⁻⁶ m³ and 1 g = 10⁻³ kg, so the ratio is 10⁻³ / 10⁻⁶ = 1,000. The [Density Converter](/density-converter/) converts between all major density units, which is useful when working with materials data sheets that mix SI and CGS unit systems.

What is terahertz radiation and where does it appear?

Terahertz (THz) radiation spans 0.1–10 THz (100 GHz–10,000 GHz), sitting between microwave and infrared on the electromagnetic spectrum. Practical uses include body scanners at airports (airport security imaging), non-destructive testing of materials, medical imaging research, and emerging 6G communications research. 1 THz = 1,000 GHz = 1,000,000 MHz. The [Frequency Converter](/frequency-converter/) covers THz alongside the more common GHz and MHz ranges.

What is the density of gold and how is it relevant to jewellery?

Pure gold (24K) has a density of approximately 19,300 kg/m³ (19.3 g/cm³). 22K gold (91.67% pure, commonly used in Indian jewellery) has a density of approximately 17,700–18,000 kg/m³. This high density is why gold feels distinctively heavy for its size — a 10 cm³ block of 24K gold weighs 193 grams. Jewellers and assayers use density to identify metal purity, since heavier-than-expected density indicates more gold content. The [Density Converter](/density-converter/) handles the conversion between g/cm³ and other units.

What angle is one turn equal to?

One complete turn = 360 degrees = 2π radians ≈ 6.2832 rad = 400 gradians. The 'turn' is occasionally used in mathematics and programming where it simplifies expressions — for example, a half-turn (180°) and a quarter-turn (90°) are more intuitive in some contexts. It also appears in typography (turning a screw one full turn) and mechanical engineering. The [Angle Converter](/angle-converter/) includes turns alongside degrees, radians, gradians, arc minutes, arc seconds, and milliradians.

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