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Suggested workflows
Use these short paths when you are not sure where to begin.
- Earthquake basics: Magnitude and energy → Moment magnitude → P-S distance → Tsunami arrival.
- Rain and water: Rainfall to volume → Open channel flow → Nutrient load → DO and BOD/COD.
- Air quality: Gas ppm and mg/m3 → AQI → Stack height → Plume model.
- Sun and horizon: Distance and bearing → Solar position → Horizon distance → Moon and tide.
- Earth interior: Geothermal gradient → Radiometric age.
- Land flow: Slope and grade → USLE erosion → Runoff estimate.
Follow each row from left to right as a suggested learning route.
Recommended tools
- Earthquake Energy Calculator: Magnitude Comparison
Use this earthquake energy calculator to compare two magnitudes and estimate how much more energy a magnitude 7 releases than 6, using E2/E1 = 10^(1.5(M2−M1)).
- Distance and bearing calculator for two latitude/longitude
Calculate distance, initial bearing, and final bearing between two latitude/longitude points with WGS84 ellipsoid or great-circle models.
- Sun Position Calculator: Solar Noon, Altitude & Azimuth
Calculate solar noon, solar altitude, azimuth, sunrise, sunset, and day length from latitude/longitude, date, time, and time zone.
- Rainfall to Volume and Flow Rate Converter
Convert rainfall (mm) and area into water volume (m³). Optionally estimate runoff volume and average flow rate (m³/s) from duration, loss, and runoff coefficient.
- ppm/ppb ↔ mg/m³ conversion (gas)
Convert gas ppm or ppb to mg/m³ and back using molecular weight, temperature, and pressure.
- P-wave / S-wave epicenter distance calculator
Estimate epicenter distance from the P-wave and S-wave arrival gap (S-P) and back-calculate the event time with a simple classroom model.
- AQI (Air Quality Index) Calculator (US EPA)
Convert 24-hour PM2.5 and PM10 concentrations (µg/m³) to US EPA AQI.
Disaster Preparedness (Earthquake, Tsunami, Ground)
Learning and estimation tools for earthquakes, tsunamis, and ground response.
- Earthquake magnitude and energy comparison calculator
Calculate the released energy ratio from two earthquake magnitudes.
- Epicenter distance and event-time estimator from P-S waves
Estimate epicenter distance from the S-P time gap and review the basic arrival-time method.
- Tsunami speed and arrival time calculator
Estimate tsunami speed and arrival time from average water depth and travel distance.
- Moment magnitude Mw calculation (fault→M0→Mw)
Calculate seismic moment M0 and Mw from fault parameters.
- Earthquake catalog b-value estimator
Create an FMD from catalog data and estimate Gutenberg-Richter b and a values.
- Liquefaction risk indicator (education)
Screen liquefaction risk using shaking intensity, groundwater level, and soil conditions.
Mapping and Terrain (Geodesy, Slope, Curvature)
Core map and terrain calculations, including geodesic distance and bearing, slope metrics, and horizon curvature.
- Distance/azimuth calculator for two latitude-longitude points
Calculate geodesic distance and initial/final bearing between two coordinates.
- Slope and angle calculator
Calculate slope (%/‰), angle (°), and slope distance from horizontal.
- Horizon distance and Earth curvature drop calculator
Approximate horizon distance and curvature drop from observation altitude.
Atmosphere and Weather (Sun, Humidity, Air Quality)
Practical atmospheric calculations for solar position, pressure-altitude conversion, humidity metrics, gas concentration, and AQI.
- Solar altitude, azimuth, sunrise, sunset, and day length
Approximate solar position and daylight timing from coordinates, date, and time.
- Pressure-altitude conversion (standard atmosphere)
Convert atmospheric pressure and altitude with ISA and sea-level correction options.
- ppm/ppb ↔ mg/m³ conversion (gas)
Specify temperature, pressure, and molecular weight to convert ppm/ppb and mg/m³.
- Dew point, wet-bulb, and heat-index calculator
Calculate dew point, wet-bulb temperature, and heat index from weather inputs.
- AQI (Air Quality Index) Calculator (US EPA)
Calculate US EPA AQI from PM2.5 and PM10 concentrations and show categories and breakpoints.
- Tide/moon phase/sunrise/sunset calculation
Show sunrise/sunset, moon phase, and tide values from shared or manual inputs.
Water (Rainfall, Flow, Water Quality)
Tools for rainfall-to-runoff estimates, open-channel flow, nutrient load, and water-quality checks.
- Rainfall to volume and flow conversion
Convert rainfall depth and area into runoff volume and flow estimates.
- Nutrient load calculation
Calculate the total load (kg) from concentration x flow rate x time.
- Open-channel flow calculator (Manning method)
Approximate flow velocity V and flow rate Q using Manning's formula.
- DO saturation, BOD/COD load, and removal calculator
Calculate DO saturation and saturation ratio from water temperature, then estimate BOD/COD load and removal.
Environmental Engineering (Dispersion, Stack, Noise, CO2)
Environmental engineering estimators for plume dispersion, stack rise, noise, and electricity-related CO2 emissions.
- Noise calculation (dB addition/distance attenuation)
Approximate combined noise level (dB) from multiple sources and distance attenuation.
- Gaussian plume dispersion calculator
Estimate concentration C(x, y, z) with a Gaussian plume model for point sources.
- Electricity CO2 emissions calculator (kWh to kg-CO2)
Estimate CO₂ emissions from electricity consumption and emission factors.
- Effective stack height calculator
Approximate plume rise and effective chimney height using Briggs formula.
Earth Interior and Age (Geothermal, Radioactivity)
Core calculations for geothermal gradient, heat flow, and radioactive decay dating.
- Radioactive decay dating calculator (half-life/ratio)
Calculate the age from the half-life and survival rate (N/N0).
- Geothermal gradient/heat flow
Calculate geothermal gradient dT/dz from temperatures at two depths and estimate heat flow.
Soil and Land (Erosion)
Simple erosion estimation based on USLE/RUSLE factors.
- USLE/RUSLE soil erosion calculator (simple)
Simple estimate of soil runoff amount using A=R×K×LS×C×P of USLE/RUSLE.
How to use this hub
- Choose one question, then use a category or the filter to find the closest calculator.
- Keep units, dates, locations, and observation conditions consistent when you compare results.
- Confirm safety, design, compliance, and reporting decisions with official guidance or a qualified professional.
FAQ
Which tool should I start with?
The quickest way is to start with purpose-specific shortcuts. For example, you can follow the steps in the necessary order, such as "rainfall → flow rate → load → water quality."
Can the calculation results be used directly for practical decisions?
No. The calculations here are for educational and approximate purposes; in practice, professional judgment is required, including observation conditions, laws and regulations, and design standards.
What does the shared URL contain?
The shared URL includes input conditions and display settings. It is not intended to be used to input personal information.
When should I leave this hub for another science section?
Leave this hub when the task becomes chemistry-heavy lab work, astronomy planning, or pure physics formulas. Stay here when the context is environmental, geologic, or field-observation based.
Related hubs
- Chemistry hubMove here when the next step is pH, concentration, solution prep, or reaction chemistry.
- Biology hubSwitch here when the interpretation turns into growth, ecology, or assay-oriented biology work.
- Science & engineering hubReturn here if you need to step back and choose a different science family.