Time Zones & Calendar Suite
High-precision astronomical, religious, business, and standardization calendar converters.
Islamic Hijri ↔ Gregorian Calendar
The Hijri calendar is a purely lunar calendar consisting of 12 months in a year of 354 or 355 days. Easily align Gregorian dates with Islamic lunar months, with support for regional astronomical sight adjustments.
Adjust by 1–2 days to match regional visual observations (e.g., Hilal sighting variations in North America, Saudi Arabia, or South Asia).
Dynamic Conversion Output
Calendar Insights
- • **Lunar Alignment**: Islamic calendars depend on physical lunar observations (hilāl). The Um Al-Qura calculation represents the official calendar of Saudi Arabia but variations occur based on geographic moon visibility.
- • **Year count**: Hijri year starts from the Hijra of Prophet Muhammad in 622 CE.
Explore Additional Utilities
Net metering — units exported ↔ bill credit estimate
Estimate utility bill credits, net energy offsets, and financial yields under 1:1 net metering or dual-rate net billing programs.
Solar irradiance — W/m² ↔ peak sun hours
Convert solar irradiance (W/m²) and daylight duration to Peak Sun Hours (PSH) and estimate daily solar panel system output.
pH adjustment — acid/alkali drops ↔ pH change estimate
Estimate acidifying or alkalizing solution amounts to safely adjust formulation pH values.
Opening altitude — deployment + snivel time → safe height
Analyze deployment altitudes, parachute snivel time/distance, and safe canopy-open hard deck limits.
Drill bit size — inches ↔ mm ↔ gauge number
Convert drill bit diameters between fractional/decimal inches, millimeters, and drill gauge number sizes.
Key length ↔ security bits — RSA vs AES equivalence
Compare security levels (bits of security) across symmetric keys, RSA, and Elliptic Curve Cryptography (ECC) based on NIST standards.
Anchor Scope Calculator
Calculate the recommended anchor rode chain and rope lengths based on water depth, vessel height, and environmental conditions.
Pipe nominal size ↔ actual OD — NPS vs DN standards
Cross-reference standard Nominal Pipe Sizes (NPS) with Diameter Nominal (DN), wall thickness, and outer diameter measurements.
Displacement tonnage ↔ cubic meters — ship buoyancy
Convert ship displacement tonnage to submerged volume (m³) and buoyancy force. Choose between freshwater and saltwater standards.
Hot water demand — occupants ↔ liters per hour needed
Estimate peak hot water demand in liters per hour and size standard water heater tanks or tankless flow rates.
Seed Sowing Rate Estimator
Calculate seed sowing rates based on target populations, thousand-kernel weight (TKW), and field survival ratios.
Soil pH & Amendment Calculator
Calculate the required lime or sulfur applications needed to correct soil acidity/alkalinity for plant growth.
Cycling FTP & Power Zone Calculator
Calculate personalized cycling power training zones (Coggan 7-zone model) based on your Functional Threshold Power (FTP) in watts.
Lactate threshold — heart rate % ↔ training zone
Convert heart rate threshold percentages into targeted cardiovascular athletic training zones.
ISO Week Number ↔ Calendar Date
Calculate ISO 8601 week numbers, week dates, and determine start/end weekdays of any given week year.
Servo angle ↔ PWM pulse width
Convert between servo rotation angle in degrees and standard PWM pulse width in microseconds, with continuous rotation presets.
Cooling & HVAC Power (BTU/h ↔ W)
Compare heating, cooling, and air conditioning power capacities with corresponding watt ratings.
Oxygen Saturation & PaO2 Converter
Convert blood oxygen saturation (SpO2) to partial pressure of oxygen (PaO2) using the clinical Severinghaus-Ellis model.
Viscosity Converter
Convert dynamic and kinematic viscosity between centipoise (cP), centistoke (cSt), Saybolt Universal Seconds (SSU), Pa·s, and m²/s.
Shrinkage allowance — finished size ↔ cut size
Calculate required pattern cut sizes from finished garment specs or expected post-wash sizes.