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Ultra-Quiet 40mm Fans

For a long time customers have asked us to stock a quiet 40mm fan, but no matter how hard we searched, we could not find one that we considered quiet enough. The problem with fans as small as 40mm is that the fan has to spin fairly quickly in order to provide any decent amount of airflow, and of course with speed comes noise. However, we are now delighted to say that we have a few products which we can thoroughly recommend for any customer who needs to replace a noisy 40mm fan in their PC.

To convert airflow in cubic feet per minute (CFM) to cubic metres per hour (m³ /h), multiply the CFM figure by 1.7.

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Noctua NF-A4x10 FLX 12V 4500RPM 40x10mm Quiet Cooling Fan

23 in stock
NF-A4x10 FLX 12V 4500RPM 40x10mm Quiet Cooling Fan
$14.26
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  • 40 x 10mm quiet PC cooling fan
  • Noise level from 12.9 dB(A)
  • Feature packed
  • Perfect for proprietary cooling
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$14.26
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23 in stock

Noctua NF-A4X10 PWM 5V 5000RPM 40x10mm Quiet Cooling Fan

252 in stock
NF-A4X10 PWM 5V 5000RPM 40x10mm Quiet Cooling Fan
$14.26
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  • 40 x 10mm 5-volt quiet PWM PC cooling fan
  • Noise level 19.6 dB(A
  • Feature packed, includes USB power adapter
  • Perfect for proprietary cooling
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$14.26
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252 in stock

Noctua NF-A4X10 5V 4500RPM 40x10mm Quiet Cooling Fan

52 in stock
NF-A4X10 5V 4500RPM 40x10mm Quiet Cooling Fan
$14.26
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  • Special 5V edition
  • 40 x 10mm quiet PC cooling fan
  • Noise level from 17.9 dB(A)
  • Feature packed
  • Perfect for proprietary cooling
More Details
$14.26
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52 in stock

Noctua NF-A4x10 PWM 12V 5000RPM 40x10mm Quiet Cooling Fan

8 in stock
NF-A4x10 PWM 12V 5000RPM 40x10mm Quiet Cooling Fan
$14.26
Add to Basket
  • 40 x 10mm quiet PWM PC cooling fan
  • Noise level from 12.9 dB(A)
  • Feature packed
  • Perfect for proprietary cooling
More Details
$14.26
Add to Basket
8 in stock

Noctua NF-A4x20 5V 5000RPM 40x20mm Quiet Cooling Fan

24 in stock
NF-A4x20 5V 5000RPM 40x20mm Quiet Cooling Fan
$14.26
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  • 40 x 20mm quiet PC cooling fan, 5V version
  • Feature packed
  • Perfect for proprietary cooling
  • From 5.5 CFM, 14.9 dBA at 5000 RPM
More Details
$14.26
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24 in stock

Noctua NF-A4x20 PWM 5V 5000RPM 40x20mm Quiet Cooling Fan

40 in stock
NF-A4x20 PWM 5V 5000RPM 40x20mm Quiet Cooling Fan
$14.26
Add to Basket
  • 40 x 20mm quiet PC cooling fan, 5V version
  • Supports fully automatic PWM speed control
  • Feature packed
  • Perfect for proprietary cooling
  • From 5.5 CFM, 14.9 dBA at 5000 RPM
More Details
$14.26
Add to Basket
40 in stock

Noctua NF-A4x20 FLX 12V 5000RPM 40x20mm Quiet Cooling Fan

68 in stock
NF-A4x20 FLX 12V 5000RPM 40x20mm Quiet Cooling Fan
$14.26
Add to Basket
  • 40 x 20mm quiet PC cooling fan
  • Three speed settings for full flexibility
  • Feature packed
  • Perfect for proprietary cooling
  • From 5.5 CFM, 14.9 dBA at 5000 RPM
More Details
$14.26
Add to Basket
68 in stock

Noctua NF-A4x20 PWM 12V 5000RPM 40x20mm Quiet Cooling Fan

130 in stock
NF-A4x20 PWM 12V 5000RPM 40x20mm Quiet Cooling Fan
$14.26
Add to Basket
  • 40 x 20mm quiet PC cooling fan
  • Supports fully automatic PWM speed control
  • Feature packed
  • Perfect for proprietary cooling
  • From 5.5 CFM, 14.9 dBA at 5000 RPM
More Details
$14.26
Add to Basket
130 in stock

Gelid Solutions Silent 4, 40mm Quiet Case Fan

260 in stock
Silent 4, 40mm Quiet Case Fan
$7.26
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  • Silent Operation
  • Optimised Fan Blades
  • High Airflow and High Static Pressure
  • Long Lifetime
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$7.26
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260 in stock

FAQ

  • How do I measure fan size?

    The size of fan you need will generally be determined by the size of the fan fitting position in your PC case. The sizes of all the fans on our website are shown as measured along any one of the fan’s four sides, NOT the distance between the fan’s screw holes! Our most popular fan size is 120mm, followed by 80mm. This isn’t really dictated by customer preference, but more by recent designs of PC cases.

    As for the thickness (depth) of the fan, generally 25mm (1 inch) is by far the most common depth, although smaller fans can have shallower depths such as 15mm or even 10mm. All our fans are 25mm thick unless otherwise stated. If you have any questions about which fan you should order, please don’t hesitate to get in touch.

    If you know the distance between the fan mounting screw holes but don’t know what fan size to order, please see the following table. Note that the mounting hole measurements shown below are taken horizontally or vertically between the holes and not diagonally.

    Screw hole spacings and fan sizes

    Space Between Screw Holes Fan Size
    32mm 40mm
    40mm 50mm
    50mm 60mm
    60mm 70mm
    72mm 80mm
    83mm 92mm
    105mm 120mm
  • I received a small cable (resistor) with my fan; what is it for?

    The resistor cable (also called Ultra Low Noise or ULN cable) is designed to allow the fan to run slightly slower for even quieter operation. The benefit in lower running noise is significant. Although the airflow will be reduced slightly, this usually has minimal effect on PC temperature. We would generally recommend using the ULN resistor cable for best results in almost all circumstances.

  • How can I tell which way the air blows through the fan?

    Hold the fan so that the round fan sticker is facing you. You are looking at the rear of the fan. When you plug the fan in, the air will be blowing towards you. If you want a fan to act as an air intake, then the fan sticker will be facing the inside of the case. Some fans also have two small arrows moulded into their plastic housing - one arrow shows the direction of airflow, and the other (at 90°) shows the direction of blade rotation.

  • Is it possible to use a 4-pin PWM fan or CPU cooler with a motherboard which has only 3-pin fan headers on it?

    Electrically, there is no problem doing this - the fourth pin on the fan cable is used purely for PWM control and is not needed in order for the fan to run. So you can plug the 4-pin fan connector onto the 3-pin motherboard fan header, leaving the fourth pin not connected to anything. The fan will potentially run at full speed, so if you would like to reduce the speed of the fan you will need to adjust the fan speed setting in your BIOS or use fan control software such as SpeedFan in Windows.

    The only other problem to consider is that occasionally, components immediately adjacent to the motherboard fan header can get in the way of the larger 4-pin fan connector, physically preventing connection. This problem also occurs if you try to use an in-line fan speed controller such as the one made by Gelid.

    Another avenue to explore is the possibility of using a bay-mounted fan controller. Several models are available now which provide 4-pin fan headers, so this is an easy way to use 4-pin PWM fans in a PC system which has only 3-pin fan headers on its motherboards. When using this method, you may find it necessary to disable any fan warning settings in your motherboard BIOS, since the motherboard may incorrectly believe that its CPU fan has failed when the fan is connected to a fan controller rather than directly to the motherboard itself.