Tools
Free calculators for water measurements
They run in your browser, with no login and no data sent. Each one is handy in the field and when interpreting results.
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Concentration unit converter
mg/l ↔ µg/l ↔ mmol/l ↔ ppm and nitrogen and phosphorus forms (NO₃ ↔ NO₃-N, PO₄ ↔ PO₄-P).
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Oxygen saturation (% saturation)
From temperature and oxygen concentration, calculate saturation in percent (with altitude and salinity correction).
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Carlson TSI calculator
Trophic state index from transparency, chlorophyll-a and total phosphorus.
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Ammonia toxicity (NH₃/NH₄⁺)
From TAN, pH and temperature, work out how much toxic NH₃ hides in the ammonia-nitrogen result.
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River discharge calculator
From depth and velocity at successive verticals, calculate discharge Q (m³/s).
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BOD5 calculator
BOD5 from initial and final oxygen - with and without dilution and a seed correction.
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Biodiversity indices calculator
From a list of taxa and abundances, calculate Shannon-Wiener, Simpson and Pielou evenness.
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BMWP-PL / ASPT calculator
Biotic index from the list of benthic macroinvertebrate families (Polish BMWP-PL variant).