Formula & worked example
COC=Ccirculating/Cmakeup; B=E/(COC−1); M=E+B+D.
At 4 cycles with 10 m³/h evaporation and 0 drift, blowdown is about 3.33 m³/h and makeup 13.33 m³/h.
HVAC engineering calculator · Updated Sep 17, 2026
Cooling Tower Cycles of Concentration Calculator — Blowdown & Makeup
Calculate cooling-tower cycles of concentration from makeup and circulating-water concentration, then estimate evaporation, blowdown and makeup flow.
Inputs
Live result
Cycles of concentration 4
Blowdown 3.3333333 m³/h
Drift 0 m³/h
Makeup 13.333333 m³/h
Assumptions & limits
- Steady-state dissolved-solids balance.
- Drift is entered separately and treatment chemistry may set a lower allowable COC.
Frequently asked questions
What does this Cooling Tower Cycles of Concentration Calculator calculate?
Calculate cooling-tower cycles of concentration from makeup and circulating-water concentration, then estimate evaporation, blowdown and makeup flow.
Is this suitable for final equipment selection?
Use it as an auditable engineering cross-check. Final selections should use measured design conditions, manufacturer data, applicable standards and local code.
Why does MAXScanner expose the assumptions?
HVAC shortcuts can hide density, pressure, concentration and effectiveness assumptions. Exposing them makes the result easier to verify and revise.