Water Cooling Calculator — PC Liquid Cooling ΔT
Find out how much your coolant temperature rises across a PC water-cooling loop. Enter the total heat load (W), the pump flow rate (L/min), the inlet temperature, and the coolant type — and get the ΔT, outlet temperature, and maximum thermal capacity at common temperature-rise limits.
W
L/min
°C
Coolant type
Outlet temperature: 26.8 °C
- 1
Mass flow rate
2 × 1 ÷ 60 = 0.0333Flow (L/min) × coolant density (kg/L) ÷ 60 = kg/s. - 2
Coolant temperature rise ΔT
250 ÷ (0.0333 × 4,186) = 1.8
How does this calculator work?
Coolant temperature rise ΔT = P ÷ (mass_flow × specific_heat). For pure water at 2 L/min and a 250 W load, ΔT ≈ 1.8°C. Glycol mixes are ~15% less efficient. A ΔT below 5°C is excellent; above 10°C, increase flow rate or radiator size. Outlet temperature = inlet temperature + ΔT.
Formula
How this is calculated
A liquid cooling loop transfers heat from hot components (CPU, GPU) to a radiator by circulating coolant. The temperature rise across the blocks — ΔT — is determined by the steady-state heat balance: the power being added (watts) equals the mass flow rate of coolant times its specific heat capacity times the temperature rise. Rearranging gives ΔT = P / (ṁ × c_p), where ṁ is the mass flow in kg/s (volumetric flow in L/min × coolant density / 60).
Pure distilled water has the highest specific heat (4186 J/kg·K) and lowest density, making it the most thermally efficient coolant. Ethylene glycol and propylene glycol 50/50 mixes reduce specific heat by about 15%, meaning for the same flow rate and heat load they produce a larger ΔT — the trade-off is freeze and corrosion protection. Practical PC loops typically run at 1–3 L/min; most air-cooled radiators can dissipate 150–300 W without raising the coolant more than 10°C above ambient.
This calculator assumes steady-state conditions and a fully mixed loop with a single coolant temperature for simplicity. Real loops have a temperature gradient from block inlet to radiator outlet. For accurate absolute temperatures, also account for radiator efficiency and ambient air temperature — the "outlet temp" shown here is the hottest point in the loop just after the heat sources.
Frequently asked questions
A coolant temperature rise of less than 5°C is excellent and typical with high flow rates and oversized radiators. A ΔT of 5–10°C is perfectly acceptable for most builds. Above 10–12°C the coolant carries significant residual heat back to the blocks, reducing their efficiency and raising CPU/GPU junction temperatures. Reduce thermal load or increase flow rate to bring ΔT down.
Yes, up to a point — ΔT drops proportionally to increasing flow. However, beyond about 3–4 L/min most radiators are already limited by airflow rather than coolant flow, so the marginal gain diminishes while pump noise and power consumption increase. A flow of 1.5–2.5 L/min is usually the sweet spot for consumer custom loops.
Water has one of the highest specific heat capacities of any liquid (4186 J/kg·K), meaning it can absorb more heat per kilogram per degree of temperature rise than glycol solutions. A 50/50 ethylene glycol mix has a specific heat roughly 15% lower, so for the same flow it produces a larger ΔT. Water is preferred thermally; glycol is added only for freeze protection and corrosion inhibition.
Also known as
TG we-Calculate Editorial Team. (2026). Water Cooling Calculator — PC Liquid Cooling ΔT [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/water-cooling-calculator
TG we-Calculate Editorial Team. "Water Cooling Calculator — PC Liquid Cooling ΔT." TG we-Calculate. 2026. https://we-calculate.com/calculator/water-cooling-calculator.
TG we-Calculate Editorial Team, "Water Cooling Calculator — PC Liquid Cooling ΔT," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/water-cooling-calculator
@misc{wecalculate_water_cooling_calculator, title = {Water Cooling Calculator — PC Liquid Cooling ΔT}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/water-cooling-calculator}}, year = {2026}, note = {TG we-Calculate} }
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