My Pond Plan
Save your pond details, carry them into the calculators, and compare plans. No account needed.
Start a Pond PlanKoi Pond Tools & Calculators
Free Koi Pond Tools
Plan, build, and maintain your koi pond
Use these free calculators for pond volume, liner sizing, circulation, waterfalls, stocking, water changes, salinity, ammonia, operating cost, and more.
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Koi Variety Quiz
Practice identifying koi by color, pattern, and scales, with explanations after every answer.
Take the Quiz💧
Pond Volume Calculator
Estimate gallons and liters for rectangular, oval, and circular koi ponds.
Calculate Pond Volume📐
Pond Liner Size Calculator
Calculate minimum liner dimensions from pond size, depth, and edge overlap.
Calculate Liner Size↻
Pond Pump Size Calculator
Estimate delivered flow, plumbing friction, and total dynamic head.
Calculate Pump Size⏱️
Pond Turnover Calculator
Calculate actual turnover from delivered flow or required flow from a target turnover time.
Calculate Turnover🌊
Waterfall Flow Calculator
Estimate delivered GPH needed for a spillway based on width and desired appearance.
Calculate Waterfall Flow🐟
Koi Stocking Calculator
Estimate a long-term koi stocking range based on pond volume and expected adult fish size.
Calculate Koi Stocking⚖️
Koi Weight Estimator
Estimate koi weight from total length using a transparent body-condition factor.
Estimate Koi Weight🚿
Water Change Calculator
Calculate replacement volume and the cumulative effect of repeated partial water changes.
Calculate Water Change🧂
Pond Salt Calculator
Calculate the salt mass needed to move from a measured current salinity to a chosen target.
Calculate Salt Amount🧪
Ammonia (NH3) Calculator
Estimate the un-ionized ammonia fraction from TAN, pH, and water temperature.
Calculate NH3🪣
Pond Fill-Time Calculator
Estimate fill time from source flow, or calculate flow with a timed bucket test.
Calculate Fill Time⚡
Electricity Cost Calculator
Estimate daily, monthly, and yearly operating cost for pumps and other pond equipment.
Calculate Electricity CostUse the calculators together
Start with pond volume, then use that result to plan circulation, turnover, stocking, water changes, and salinity calculations. The ammonia tool adds pH and temperature to estimate how much measured total ammonia is in the more toxic un-ionized NH3 form.