Flow Rate Estimator Spreadsheet                       

This page is dedicated to providing updates and development of a flow rate estimator spreadsheet.  This spreadsheet was created to help other water coolers with estimating their flow rate.  I'll be providing updates to the estimator here.

What is it?  How does it work?                    

It is an educational excel file I wanted to share with you to lean how different water cooling components affect system flow rate. It's important to keep track of all the different parts in a water cooling system and make sure you have enough flow rate.  Many components including water blocks and radiators have thermal efficiency curve where they cool better as flow rates increase.  This is generally because the water within them is more turbulent so more mixing of water occurs.  If water moves very slowly, there is less contact with the surrounding metal to transfer heat.  These days, the pumps we have available to use make flow rate less of an issue, but I still think it is very interesting and educational to understand.  I have some general rules of thumb for flow rate to help guide you.  While it's pretty difficult to get a system below 1 gallon per minute with a Laing D5 or DDC pump, it is possible if you put too much restriction into the loop.

All this spreadsheet does is calculates a pumping curve based on curves from products I have tested, and it adds up the system pressure drop curves.  A system flow rate is determined by the intersecting point of the pump and system pressure drop curves, that's what this spreadsheet does.  It calculates both curves, finds the intersecting point, and returns a flow rate.


This is for educational purposes only!  If there is any particular curve you think is out and you have some better or more current information, please let me know and I'll update this tool. I've seen results off as far as 15-20%, so it's just an estimate.  There are other errors like viscosity added by coolant dyes, voltage differences in power supplys, etc, that will also have some impact.  Finally, by popular demand I have included the curves that were developed by other users and added a note (Error, not tested!) to those curves.  These products were not tested by myself, therefore there is a high probabilty relative results will have a high error, and I would HIGHLY recommend not using the tool particularly these products for comparison purposes.  There is likely a very big difference in results between my own testing and those of others, it is always best to only compare products that were tested on the same test bed with the same equipment and methods.


  • Version 3.1 is out!  Added the the prototype SWC DDC3.2 top, retested the Laing D5, added the new EK D5 X-Top, added back in the old D5 setting 1-4 tests (temporary), added in the TFC 480ER radiator, and some minor cleanup work.


By clicking the link below you understand:
  • Educational spreadsheet for educational purposes only
  • Pressure drop curve database was developed from internet sources and may be in error.
  • Estimator has been shown to be in error by as much as 20%
  • Author is not responsible for accuracy or error.
  • Use this information at your own risk!
Excel 97-2000 spreadsheet zipped

How much flow rate is enough?

I have alot of people ask me..."how much is enough?".  I've had a rule of thumb in the estimator for a while now, but I'm not entirely happy with that knowing that "enough" means something different to everyone.  In general the effect of flow rate is fairly small in comparison to the gain you might get from increasing your radiator size, but it's something you have decent control over, so it's always talked about.  To help clarify the effects of flow rate, I decided to use some c/w curves and put together a chart for a 200 watt load and 110 watt load to try to capture a feel for this and allow you to make that determination yourself.  Keep in mind there is no standard for c/w curves on waterblocks, so don't pay attention to the actual value as much as the difference between different flow rates.

This doesn't take heat dump into account from the pump, but that is also a very important consideration.  Every now and then I'll see someone post a large irrigation pump on the forums asking if it will work.  When only 40 watts of added heat can be responsible for .8C on a triple radiator, 1.9C on a double, or 2.8C on a single radiator...it quickly becomes clear that pump heat dump is extremely important when compared to the gain in flow rate.  That's why I would recommend that you match your pump to the components.  You want the least amount of pump heat dump to provide you adequate flow rates, it's a careful balance.  I generally try to shoot for 1.5GPM just so you have some reserve capacity to add more blocks in later, but it's not a real magical number.

Bottom line:

  • Single block loop = Flow rate is of low importance, slight impact to radiator performance only
  • Multiple block loop = Flow rate of moderate importance, impact to radiator performance as well as other blocks.  In addition, water temperature gain across blocks increases as flow rate reduces further impacting blocks further down the same loop.

Here is that look using the D-Tek Fuzion c/w curves as a basis for comparing actual impact from flow rate.  Generally blocks with large open channels will have more impact by flow rate than those with small and fine pins.

Components Version 3.1

Blue indicates new or updated curves

CPU Blocks:
Aqua Extreme MP-05  N3 (NOT TESTED! ERROR!)
Aqua Computers Double Impact
Danger Den MC-TDX
Danger Den TDX, Nozzle #1
Danger Den TDX, Nozzle #2
Danger Den TDX, Nozzle #3
Danger Den TDX, Nozzle #4
Danger Den TDX, Nozzle #5
D-Tek Fuzion V1 - 3.6mm Nozzle + Washer
D-Tek Fuzion V1 - 4.4mm Nozzle + Washer
D-Tek Fuzion V1 - 5.5mm Nozzle + Washer
D-Tek Fuzion V1 - 6.3mm Nozzle + Washer
D-Tek Fuzion V1 - Quad Nozzle + Washer
D-Tek Fuzion V1 - Stock + Washer
D-Tek Fuzion V1 - Stock
D-Tek Fuzion V2 - 3.6mm Nozzle
D-Tek Fuzion V2 - 4.4mm Nozzle
D-Tek Fuzion V2 - 5.5mm Nozzle
D-Tek Fuzion V2 - 6.3mm Nozzle
D-Tek Fuzion V2 - Quad Nozzle
D-Tek Fuzion V2 - Stock
D-Tek Whitewater LE (NOT TESTED! ERROR!)
EK Supreme
Stinger V8
Swiftech Apogee (NOT TESTED! ERROR!)
Swiftech Apogee GT (NOT TESTED! ERROR!)
Swiftech Apogee GTX (NOT TESTED! ERROR!)
Swiftech MCW-6002 (NOT TESTED! ERROR!)
Swiftech Storm (NOT TESTED! ERROR!)
Thermalright XWB-01
XSPC Edge Acrylic CPU Prototype
GPU Blocks:
Danger Den IONE 8800GT/GTS G92
Danger Den 8800GTX
Danger Den Maze 5
D-tek Fuzion GFX
EK FC-3850/3870
EK FC-88 (G92) (8800GT)
Swiftech MCW-60
Swiftech Stealth Rev2 (NOT TESTED! ERROR!)
XSPC Razor 3870
Danger Den Maze 4 (NOT TESTED! ERROR!)
Danger Den MPC-680i
Danger Den MPC-Universal
Swiftech MCW-30
XSPC X20 Delta Chipset
EK Mosfet Asus 3a
Fittings & Tubing:
Elbow 1/2" Nylon
Elbow DD Derlin 90
Elbow DD Acrylic 90
Elbows Copper 1/2"-5/8" Barb
Reservoir (1/2" Barb)
T  (1/2" Nylon Fitting)
T (5/8" Nylon Fitting)
DD Delrin Tee
DD Acrylic Tee
Tee Copper 1/2" 5/8" Barb
Tubing 10' 3/8" ID Tubing Tested
Tubing 10.16' 7/16" Tubing Tested
Tubing 10.58' 1/2" Tubing Tested
Heatercore '77 Bonnie
HW Labs BIX 120 or  240 (NOT TESTED! ERROR!)
HW Labs 480 GTX
Swiftech MCR-120 QP G1/4(NOT TESTED! ERROR!)
Swiftech MCR-220 QP G1/4 (NOT TESTED! ERROR!)
Swiftech MCR-320 QP G1/4 (NOT TESTED! ERROR!)
Swiftech MCR-320 QP 3/8" NPT W/ 5/8" Barbs
The Feser Company (TFC) X-Changer 360
The Feser Company (TFC) X-Changer 480
Thermochill PA 120.2 (NOT TESTED! ERROR!)
Thermochill PA 120.3
Thermochill PA160 (NOT TESTED! ERROR!)
DigiFlow 8000T Flow Rate Meter
Swiss Flow SF800
Alphacool AP1510, 24V
Alphacool AP1510, 21V
Alphacool AP1510, 18V
Alphacool AP1510, 15V
Alphacool AP1510, 12V
AquaExtreme 50Z (NOT TESTED! ERROR!)
Danger Den CPX-Pro
Eheim 1048 (NOT TESTED! ERROR!)
Eheim 1250 / Hydor L30 (NOT TESTED! ERROR!)
Iwaki MD20Z (50Hz/220V) (NOT TESTED! ERROR!)
Iwaki MD20Z (60Hz/115V or 220V)(NOT TESTED! ERROR!)
Iwaki MD30Z (50Hz/220V)(NOT TESTED! ERROR!)
Iwaki MD30Z (60Hz/115V or 220V)(NOT TESTED! ERROR!)
Iwaki RD-20, 24V (NOT TESTED! ERROR!)
Iwaki RD-30, 24V
Iwaki RD-30, 21V
Iwaki RD30, 18V
Iwaki RD30, 15V
Iwaki RD30, 12V
Laing D5 Vario, Setting 1, 12V, =MCP655 (NEEDS RETESTED)
Laing D5 Vario, Setting 2, 12V, =MCP655 (NEEDS RETESTED)
Laing D5 Vario, Setting 3, 12V, =MCP655 (NEEDS RETESTED)
Laing D5 Vario(Basic), Setting 4, 12V, =MCP655B (NEEDS RETESTED)
Laing D5 Vario, Setting 5, 12V, =MCP655
Laing D5 Vario, Setting 5, (w/EK D5 X-Top)
Laing DDC-1 18W (Stock)(NOT TESTED! ERROR!)
Laing DDC-1 18W (w/Alphacool Pro-Res Top)(NOT TESTED! ERROR!)
Laing DDC-1 18W (w/Alphacool Pro-Top)(NOT TESTED! ERROR!)
Laing DDC-1 9W (Stock)(NOT TESTED! ERROR!)
Laing DDC-1 9W (w/Alphacool Pro-Res Top)(NOT TESTED! ERROR!)
Laing DDC-1 9W (w/Alphacool Pro-Top)(NOT TESTED! ERROR!)
Laing DDC-2 (w/DDCT-01s top)(NOT TESTED! ERROR!)
Laing DDC-2(Stock)(NOT TESTED! ERROR!)
Laing DDC-3.1 (stock)=MCP350
Laing DDC-3.1 (w/Alphacool Plexi Top) Top Inlet
Laing DDC-3.1 (w/Alphacool Reservoir Top)
Laing DDC-3.1 (w/Danger Den Top) Top Inlet
Laing DDC-3.1 (w/EK G1/4 X-Top)
Laing DDC-3.1 (w/EK G3/8 X-Top)
Laing DDC-3.1 (w/Koolance Top) Top Inlet
Laing DDC-3.1 (w/OCLabs XPTop)
Laing DDC-3.1 (w/Petra DDCT-01s Top)
Laing DDC-3.1 (w/XSPC DDC Top)
Laing DDC-3.1 (w/XSPC Reservoir Top)
Laing DDC-3.2 (stock)=MCP355
Laing DDC-3.2 (w/Alphacool Plexi Top) Top Inlet
Laing DDC-3.2 (w/Alphacool Reservoir Top)
Laing DDC-3.2 (w/Danger Den Top) Top Inlet
Laing DDC-3.2 (w/EK G1/4 X-Top)
Laing DDC-3.2 (w/EK G3/8 X-Top)
Laing DDC-3.2 (w/Koolance Top) Top Inlet
Laing DDC-3.2 (w/OCLabs XPTop)
Laing DDC-3.2 (w/Petra DDCT-01s Top)
Laing DDC-3.2 (w/SWC Prototype Blue Top)
Laing DDC-3.2 (w/XSPC DDC Top)
Laing DDC-3.2 (w/XSPC Reservoir Top)
Sicce Nova 800(NOT TESTED! ERROR!)
Swiftech Apogee Drive Stock (DDC3.1 w/ Apogee GT)
XSPC Dual Bay Reservoir Pump