You are measuring the courtyard. The actual component will cover the “height” of the pad and extend from the midpoint(ish) of the two pads
The center of one pad to the center of the other pad looks like 1mm.
Pads need to be big enough to mechanically support and provide reliability for use of the product.
Check out some manufacturers data sheets for their recommendations.
Hand solder pads are usually a little larger to make mounting and soldering easier.
And as @thebigg has pointed out, there is the courtyard, which is not the copper pad, but the clearance settable by you.
The pads are larger with the hand solder variant to make it easier to solder with an iron as opposed to manufactured with a machine
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Also, with PCB Editor / View / 3D Viewer [Alt + 3] you open KiCad’s 3D viewer and this makes it easier to see what you are seeing.
You are measuring the courtyard not the part. If you view the Fab layer you will see the outline of the part itself which you can also measure. This will show the dimensions you expect.
0402 footprints can’t be positioned in 1mm/0.5mm grid array. Imagine them touching each other - how would you ensure not shorting between their pads? The rectangle you measure includes needed margin. If possible I place footprints at my PCB with that rectangles touching each other to minimize the occupied area.
I don’t use hand solder footprints, and in rare cases when I need hand de-solder and solder of elements (mainly 0603) i have no big problem with it.
Hand solder footprints have longer pads to give you extra space to touch it with soldering iron tip.
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A handsolder pad extends far enough beyond the component that the iron tip can touch the pad and miss the end cap. This margin starts getting very wasteful at the 0603 and smaller levels
Thanks, so is it necessary to select parts package with ‘‘Handsolder’’ if the parts will be finally attach to the board per hand ? Or it’s depends on the ablitiy of the ‘‘solder person’’ ? The dimension of the package will always be same, even the handsolder package has lagger pads right ?
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Yes, that is also an important factor.
I don’t understand why you ask this question. If you buy a part with a certain size, then it’s size won’t suddenly change depending on how you design the PCB.
But most importantly, in your first post:
0402 is a quite small package. Most people find this difficult to (hand) solder parts of this size without specialized equipment. Apparently you have very little experience with PCB design and sizes of parts. Therefore I suggest you start with something like: https://duckduckgo.com/?q=smt+soldering+practice+kit&iax=images&ia=images With such a kit and parts in different sizes, you can get some feeling for what it is to (hand) solder those parts, and with different sizes you can also experience where your own abilities are.
If you don’t want to spend money on such a kit, then take apart some random electronics PCB’s. Solder off some of the parts, clean the pads with flux and desoldering braid and then solder the parts back on. Experiment with several PCB’s and parts in different sizes.
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Hello, thanks for the support. Yes you are right, I don’t have much experience at PCB designing or manufacturing. I am doing a PCB designing and afte that the layout would be sent to somewhere else to be fabricated, so my soldering ability might not be the most important factor in this situation right ? In this designing there are plenty of bypass capacitors which according to the datasheet should be as close as possible to the parts, so I am using small package like 0402 for capacitors to make the PCB more compact. Based on my knowledge I don’t except too much of the equipment or the ability of the person who do the soldering, and you have mentioned that 0402 is already too small to most people. In order to maintain the schedule I am thinking about to make a plan B in advance : by using a larger package, or would a handsolder package with same package size make a difference ? Becaues I think it would be meaningful to keep the PCB compact. 
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We (small firm) use mainly 0603 elements except that bypass capacitors we use 0402 as they have to be located close to ICs and if 0603 is there it disturb connection to neighboring pads.
I use 0603 because I can route track under it, what helps to design 2 layer PCB with whole bottom being GND. I can’t route track under 0402 but connections to bypass capacitors rather not crosses with other connections.
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Thanks,so would it be much easier for the solder person, if I keep the old size (0402) but chose the handsolder package ?
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Again this depends on the ‘solder person’ as to how small you can go. I have a few years under my belt and unless there is a good reason to go very small I stick to 0805 and ‘hand soldered’ I do this because I don’t want to give myself a hard time without a good reason ! 
It depends on my design criteria as well. A cheap kit (as recommended) is a great idea if you are to become a ‘solder person’ if you are not then you need to know who is and if its one of the Chinese PCB makers check the capabilities section. If you have little to no SMD soldering experience and you use 0402 you are going to have a very bad day 
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Indeed. 0805 is quite easy. 0603 is still “doable” by most persons and some equipment but 0402 (and smaller) starts getting difficult. Commercial P&P machines also have a few limits. There is a difference between the minimum size they can handle, and what minimum size they can handle reliably. The only good answer I can give here is that you should ask your “solder person” questions like these.
I also think it’s still educational if you get such a solder practice kit to get some more insight in the sizes of the things you are dealing with. At the moment I am not even sure whether you do even have a (any kind of) soldering iron yourself (or used one).
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There is also a reference sheet created by @JohnRob lower down in this forum that @LF666 may wish to print:
SMD Size Chart
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I don’t find the handsolder versions that much easier to solder, it’s more important to not pack the components too tightly on the PCB.
0603 is easy to solder with standard equipment like good tweezers and a small, good soldering iron (e.g. a pinecil). 0402 can technically be soldered with the same equipment, but will be more finicky, to be more comfortable, you need proper equipment for micro soldering, like a hot plate, a hot air station, ideally a microscope, high quality flux, and so on.
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I second that, don’t just rely on the flux in your solder.
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I would think the fabricator/manufacturer of the PCB will use a pick and place machine and a oven to “solder”, so there may not require any hand soldering. But if for some reason they do this for prototypes or reworking the board then it would be something to consider
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So you think of using hand soldering footprints for reflow soldering if reworking is considered.
I’m not sure if it is good solution. I don’t know what situation generates small elements standing up (on one their end) during reflow soldering. May be wrongly distributed surface tension caused by bigger pads can be the reason. I just don’t know - I have never tried using in reflow other pads than suggested by manufacturer for reflow. I don’t see a problem with reworking when footprints destined for reflow soldering are used.
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