How much radiator surface area do I need for an RTX 4090 or 5090 and Core i9-14900K?

An overclocked Core i9-14900K (300W+) paired with an RTX 4090 or RTX 5090 (450W–600W) generates between 750W and 950W of peak heat. To maintain a 10°C coolant-to-ambient Delta-T at quiet fan speeds (800–1,000 RPM), you need a minimum of two 360mm radiators (720mm total length) or two 420mm radiators.

Should I choose a D5 or DDC pump for my custom water cooling loop?

A single D5 pump is the gold standard for most dual-radiator CPU + GPU loops, offering high flow volume (up to 1,500 L/h) and silent operation cooled directly by the liquid. However, if your loop includes 3+ micro-channel water blocks, multiple 90-degree rotary fittings, or quick-disconnects (QDCs), a high-head-pressure DDC pump or dual D5 pumps in series are required to keep flow rates above the 0.8 GPM minimum threshold.

What is a safe water coolant temperature and Delta-T in a custom loop?

Enthusiast loops aim for a 10°C Delta-T (meaning if your room ambient is 22°C, your coolant runs at 32°C). Coolant temperatures must never exceed 50°C (122°F) if using PETG hardline tubing to prevent tube deformation and fitting blowouts, or 60°C for D5/DDC pump motor longevity.

Custom PC Water Cooling Radiator & Pump Sizer

Calculate total thermal dissipation (Watts), required radiator surface area at a 10°C Delta-T, fan static pressure, and D5 vs. DDC pump head restriction.

1. Hardware Thermal Load (TDP)

CPU Model Preset (or enter custom Watts below):

CPU Peak Thermal Load (Watts): Actual PL2 / PBO package power draw under full all-core load.

GPU Model Preset (or enter custom Watts below):

GPU Peak Thermal Load (Watts): Total board power draw (multiply by 2 for dual-GPU rendering nodes).

Overclocking / Power Limit Headroom (%): Percentage thermal increase from raised voltage or unlocked BIOS power limits.

2. Acoustic & Loop Restriction Profile

Target Fan Acoustic Profile (@ 10°C Coolant ΔT): Determines how much heat each 120mm radiator section can dissipate quietly.

Number of 90° Rotary Elbows & Quick-Disconnects (QDCs): Sharp 90° bends and QDC valves add significant hydraulic head restriction.

Micro-Channel CPU Water Block (High jet-plate restriction) Full-Cover GPU Water Block (Medium-high fin restriction) Motherboard Monoblock / VRM / RAM Block Case Distribution Plate (Distro Plate with 90° internal channels)

3. Engineered Loop Specifications

Recommended Radiator Configuration:

Enter specs to calculate

Target: 10°C Coolant-to-Ambient Delta-T (ΔT)

Total Peak Loop Heat Dissipation (Incl. 20W Pump):

0 W

CPU: 0W | GPU: 0W | Overclock: +0W | Pump: 0W

Pump Architecture & Head Pressure Spec:

0.0 m H₂O Head

Select loop water blocks and fittings to compute restriction.

Minimum Fan Static Pressure & Radiator Core:

0.0 mm H₂O

Required to push air through 14–16 FPI copper radiator fins.

Custom Water Cooling Radiator Dissipation & Pump Sizing Matrix (10°C ΔT)

Reference heat dissipation capacity across standard copper radiator sizes at a 10°C water-to-air Delta-T, alongside recommended pump architectures:

Radiator Size	Core Surface Area	Silent (800 RPM)	Balanced (1,300 RPM)	Performance (1,800 RPM)	Min Fan Static Pressure	Recommended Pump
240mm (2×120mm)	28,800 mm²	~140 Watts	~210 Watts	~290 Watts	1.8 mm H₂O	Single DDC or D5 PWM
360mm (3×120mm Slim 30mm)	43,200 mm²	~210 Watts	~315 Watts	~435 Watts	2.0 mm H₂O	Single D5 PWM Combo
420mm (3×140mm Standard)	58,800 mm²	~280 Watts	~410 Watts	~540 Watts	2.2 mm H₂O	Single D5 PWM Combo
Dual 360mm (6×120mm 45mm Thick)	86,400 mm²	~450 Watts	~650 Watts	~880 Watts	2.5+ mm H₂O	High-Flow D5 or DDC 3.2
Triple 360mm / External MO-RA3	129,600+ mm²	~700+ Watts	~980+ Watts	~1,300+ Watts	2.8+ mm H₂O	Dual D5 in Series

Frequently Asked Questions

How much radiator do I need for an RTX 4090 / 5090 and Core i9-14900K?

A flagship CPU and GPU combination outputs 700W to 900W under heavy gaming or AI rendering workloads. While a single 360mm radiator can technically prevent thermal throttling with fans screaming at 2,200 RPM, maintaining a quiet 800–1,200 RPM acoustic profile with a safe 10°C water Delta-T requires at least Dual 360mm radiators (720mm total) or Dual 420mm radiators.

What is the difference between a D5 and a DDC water cooling pump?

A D5 pump uses a spherical ceramic bearing cooled directly by the loop fluid, delivering massive flow volume (~1,500 L/h), near-silent operation, and ~3.9 meters of head pressure. A DDC pump is smaller and air-cooled from underneath, trading total volume for superior head pressure (up to 5.2+ meters), making DDC ideal for SFF builds or restrictive loops with multiple blocks and quick-disconnect fittings.

Why does radiator thickness (30mm vs. 45mm vs. 60mm) matter for fan choice?

Slim 30mm radiators have lower air resistance and perform best with low-RPM fans (800–1,100 RPM). Thick 45mm to 60mm radiators pack more copper surface volume, but require high static pressure fans (>2.5 mm H₂O) or a push-pull fan configuration to prevent air from stalling inside the fin stack.

Verified Custom Loop Radiators, Pumps & High-Pressure Fans

Radiator Core

Copper Water Cooling Radiator

High-efficiency pure copper fin radiator sized to match your thermal dissipation and acoustic profile.

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Pump & Reservoir

D5 / DDC PWM Pump Reservoir

Precision PWM pump-reservoir combo engineered to maintain >0.8 GPM flow across micro-channel blocks.

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Static Pressure

High Static Pressure Radiator Fans

Focused blade geometry delivering >2.5 mm H₂O static pressure to push air cleanly through dense radiator cores.

Shop High-SP Radiator Fans

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Engineering & Hardware Safety Disclaimer: Calculations generated by this utility are thermodynamic and fluid-dynamic estimations intended for planning and educational purposes only. Actual coolant temperatures, flow rates, and head pressure drops vary based on ambient room temperature, case airflow restriction, fin density (FPI), and coolant viscosity. Always leak-test custom liquid cooling loops with an air pressure tester prior to powering electronics, and monitor inline coolant temperatures to prevent PETG/acrylic tubing deformation.