Science
1,125 science calculators for chemistry, physics, biology, astronomy and the Earth sciences. Each one states the relation it uses and the units it expects, so class problems, lab work and quick checks come out right, free in your browser.
Y-Linked Inheritance Probability Calculator for Sons and Daughters
Shows how a Y-chromosome trait travels: an affected father passes it to 100% of his biological sons and 0% of his daughters, because daughters receive his X…
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Dry air density calculator
Enter absolute pressure and temperature, such as the sea-level reference of 101325 Pa and 288.15 K, and get the density of dry air in kg/m³ from the ideal gas…
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Air density ratio to sea level calculator from pressure and temperature
Compare your air with sea-level air at 101325 Pa and 15 °C: a ratio of 0.80 means about eighty percent of that density, and 1.10 means about ten percent denser.
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Surface Albedo Reflected Radiation Calculator
Find how much sunlight a surface sends back: 800 W/m² on an albedo of 0.3 reflects 240 W/m² and absorbs 560 W/m².
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Air quality index from carbon monoxide
An eight-hour carbon monoxide average of 4 ppm equals AQI 45, in the Good category, on the official US EPA table.
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Gutenberg-Richter b Value Calculator
Measure how steeply earthquake counts fall as magnitude grows: six events, complete from magnitude 2.1 and reported in 0.1 bins, give a b value just over three…
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Betz Limit Maximum Wind Power Calculator
See the physical ceiling on wind power: a 100 m² rotor in a 10 m/s wind can capture at most 36.32125 kW, or 59.3 % of the power in the moving air.
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Flight carbon footprint calculator
Put a number on one seat’s climate impact: 5500 km in economy with the default factors comes to 1201.75 kg of CO₂e.
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Climate Running Mean Smoother Calculator
Smooth noisy climate data without shifting it in time: seven yearly values with a 3-point window give 5 centered means, the first aligned with index 1 and the…
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CO2 Offset Tree Equivalent Calculator
Picture a CO2 total as trees: 1000 kg at 22 kg per tree each year equals 45.45 tree equivalents, so 46 whole trees would be needed.
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Coriolis parameter calculator
Turn a latitude into the Coriolis parameter: at 45° north, f is 0.000103126079 per second with Earth's rotation rate.
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Effective growing degree days calculator
Count only the heat crops can use: with a base of 10 and a cutoff of 30, three days of 28/12, 32/18 and 22/8 add up to 30 effective degree days.
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Density altitude from pressure altitude and temperature calculator
See how heat thins the air for flying: a pressure altitude of 5000 ft at 30 °C is 24.906 °C above standard and gives a density altitude of 7800.726033 ft.
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Sonntag 1990 dew point calculator from temperature and humidity
Turn a temperature and humidity reading into a dew point: 25 °C at 60 % relative humidity gives 16.701894 °C, with vapour pressures of 31.699039 and 19.019424…
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Diurnal temperature range calculator
Measure how much your days swing between warm and cool: highs of 28, 30 and 26 with lows of 12, 14 and 11 give daily ranges of 16, 16 and 15, a mean of fifteen…
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Equivalent potential temperature calculator
Compare moist air parcels on one scale: air at 300 K and 1000 hPa holding 10 g/kg of vapour has an equivalent potential temperature of 331.127577766795 K.
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Blaney-Criddle evapotranspiration calculator
Estimate crop water demand from just two climate figures: a mean temperature of 20 °C gives a temperature factor of 17.2, which is multiplied by the daytime…
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Hargreaves-Samani ET0 calculator
Get reference evapotranspiration from temperature records alone: a day of 12 to 28 °C, mean 20 °C, with radiation of 35 mm/day gives an ET0 of 12.1716 mm/day.
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Ship Froude number calculator
Compare hull speed with the waves the hull makes: a 100 m waterline at 10 m/s gives a Froude number of 0.31933, in the transition band where wave-making…
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Geopotential to Geometric Height Calculator
Turn a gravity-normalized height into real distance: a geopotential height of 10000 m sits more than fifteen metres higher in geometric terms.
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Greywater Reuse Water Savings Calculator
Reusing 450 liters of greywater at an efficiency of 0.8 saves 360 liters of drinking water, and the other 90 liters appear as unrecovered so the balance always…
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Growing degree days calculator
A day with a low of 50 °F and a high of 86 °F averages 68 °F, so against a 50 °F base it adds 18 growing degree days.
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Growing Season Length Calculator from Daily Frost Data
If the last spring frost falls on April 10 and the first autumn frost on October 20, your growing season lasts 193 days.
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Simplified heat index calculator
At 86 °F and 65 % relative humidity, the simplified heat index comes out at 87.36 °F, a quick reading of how muggy air adds to the heat.
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Steadman apparent temperature calculator with wind and radiation
At 30 °C, 65 % humidity, 2.5 m/s of wind and 120 W/m² of net radiation, conditions feel like 40.29 °C, and you see how much humidity, wind and sun each added or…
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Heat Pump Output from COP Calculator
A heat pump drawing 2.5 kW at a COP of 3.8 delivers 9.5 kW of heat, and the result keeps whatever unit you entered, so kilowatt-hours in give kilowatt-hours…
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Hydraulic conductivity from permeability calculator
Hydraulic conductivity follows from K = kρg/μ: enter permeability in m², water at 998.2 kg/m³ and 0.001002 Pa·s, and standard gravity of 9.80665 m/s² fills in…
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Hydraulic Radius of Channel Calculator
Divide 12.5 m² of flow area by 8.2 m of wetted perimeter and you have the channel's hydraulic radius, in meters.
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Solar inverter sizing calculator
A 7200-watt solar array at a DC-to-AC ratio of 1.2 points to an inverter of 6000 watts, or 6 kW. Use it to compare design ratios early and keep the arithmetic…
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Koppen Climate Classification Calculator
Twelve months averaging 26.68 °C with 2560 mm of rain a year classify as Af, tropical rainforest, and you see the aridity threshold of 673.5 mm and the coldest…
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Landfill methane generation calculator
Enter 10000 Mg of waste, a methane potential of 100 m³ per Mg, a decay rate of 0.05 per year and an age of 10 years to see that year's methane rate, the total…
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Lifting condensation level temperature calculator
Surface air at 30 °C with a 20 °C dew point becomes saturated at 17.665117 °C when lifted: that is the lifting condensation level temperature, shown in Celsius…
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Longshore sediment transport rate calculator
Waves breaking 1.5 m high at 15 degrees from the shore-normal give sin(2α) = 0.5, and with the default K of 0.39 the CERC formula turns that into a longshore…
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Earthquake energy ratio between magnitudes calculator
A magnitude 7 earthquake releases about 998.56 times the energy of a magnitude 5, because each whole step multiplies energy by roughly 31.6.
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Manning Open-Channel Discharge Calculator
Enter a roughness of 0.03, a hydraulic radius of 1.2 m, a flow area of 4.5 m² and a bed slope of 0.002, and Manning's equation returns the channel's discharge…
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Atmospheric moisture flux calculator
Air holding 0.01 kg of water vapor per kg and moving at 10 m/s carries a horizontal moisture flux of 0.1, the product of specific humidity and wind.
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Annual pluviometric index calculator
Twelve months adding up to 1260 mm against a long-term mean of 1200 mm give a pluviometric index of 105, five percent above normal and classed as near the mean.
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Radiometric age calculator
Equal amounts of parent and daughter isotope, a ratio of 1, with a decay constant of 0.1 per year give an age of 6.9314718056 years, exactly one half-life.
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Uranium-lead radiometric age calculator
A 206Pb/238U ratio of 0.1 gives an age of roughly 614 million years with the Steiger and Jäger 1977 decay constant.
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Refrigerant leak CO2 equivalent calculator
A 2.5 kg refrigerant leak with a global warming potential of 1430 equals 3575 kg, or 3.575 tonnes, of CO2 equivalent.
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Relative humidity from specific humidity
At sea level, a specific humidity of 0.0072 kg/kg at 20 °C and 1013.25 hPa means a vapor pressure near 11.7 hPa against a saturation pressure near 23.4 hPa…
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Richter magnitude from amplitude calculator
A 1 mm trace amplitude recorded 100 km from the epicentre gives a local magnitude of 3, after a distance correction of 3.
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Atmospheric scale height calculator
Air at 288.15 K with a mean molar mass of 0.0289644 kg/mol under 9.80665 m/s² of gravity has a scale height of a little over eight kilometres, shown in metres…
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Seawater density calculator from salinity, temperature and pressure
Seawater at 35 PSU and 15 °C has a density of 1025.972754 kg/m³ at the surface and 1030.657561 kg/m³ under 1000 dbar, roughly 1000 metres down.
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Sediment compaction porosity calculator
Sand starting at 0.5 porosity, buried 2 km with a compaction coefficient of 0.5 per km, keeps just over eighteen percent pore space, a little over a third of…
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Sediment Accumulation Rate Calculator
12.5 metres of sediment between horizons dated 18,500 and 6,000 years before present built up over 12,500 years, an average of 1 millimetre per year.
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Radiation shielding half-value layer calculator
A shield three half-value layers thick, 7.5 against a half-value layer of 2.5 in the same unit, cuts an intensity of 1000 to 125: a transmission of 0.125 and…
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Significant wave height calculator
Paste the wave heights from a record and get Hs, the average of the highest third: nine waves topped by 2.4, 2.1 and 1.8 give an Hs of 2.1 in the same unit.
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Snow-to-liquid ratio calculator
At a 10:1 ratio, 0.5 inches of liquid water becomes 5 inches of snow; enter a measured snow depth instead and you get the ratio that actually fell.
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Solar panels needed for net zero
If your home uses 4000 kWh a year and each panel yields 400 kWh, you need 10 panels to reach net zero.
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Solar Panel Payback Period Calculator
Divide what the installation really costs after incentives by what it saves on bills each year: a ratio of 7.5 reads as 7 years and 6 months, or 90 months.
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Solar panel power output calculator
Sunlight of 1000 W/m² on a 1.6 m² panel at 20% efficiency gives 320 W, or 0.32 kW. Use it to check a datasheet claim or size an array before adding real-world…
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Groundwater Specific Discharge Calculator
With a conductivity of 0.0001 m/s, a gradient of 0.02 and a porosity of 0.25, specific discharge is 0.000002 m/s and water moves through the pores at 0.000008…
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Specific humidity to mixing ratio calculator
A specific humidity of 0.012 kg/kg becomes a mixing ratio slightly above 0.012, because the vapor is measured against dry air alone instead of all the moist…
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Tidal prism volume calculator
An estuary of 2500000 m² with a 1.8 m tidal range exchanges 4500000 m³ of water between low and high water.
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True wind from apparent wind calculator
With 18 knots of apparent wind at 45° off the bow, a boat speed of 6 knots and a 90° heading, the true wind is 14.396699 knots from 152.139272° true.
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Recycling CO2 savings calculator
Recycling 1250 kg of material with a factor of 0.85 kg CO2e per kg avoids 1062.5 kg CO2e, or 1.0625 tonnes.
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Absolute water vapor density calculator
A vapor pressure of 2339 Pa at 293.15 K, about 20 °C, means roughly 17.3 grams of water vapor in every cubic metre of air.
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Ocean Wave Group Velocity Calculator
A 100 m wave in 20 m of water carries its energy at just over 8 m/s, while its crests run faster, at more than 11 m/s.
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Deep-water wave celerity from period
A 10-second swell in deep water travels at about fifteen and a half metres per second, with crests roughly one hundred fifty-six metres apart.
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