I'd like to be able to estimate better how much time a LEGO set will take me to build. Are there any resources online that indicate average or fastest building times for a given set? I suppose it also depends on type of set (for younger or for adult builders, Technic or System,...) What would be your estimate given the amount of elements in a set and type of set?

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    Do you have couple of sets in mind? Time it takes to build will wildly depend on experience (how much you know your elements and their colors) and the type of parts you have in a set. Building biggest Technic sets for the first time will take considerably longer than having it as, say, 5th build. And even if you building same sized (parts wise) Technic/System/Creator/Mosaic set each will take different amount of time.
    – Alex
    Mar 13, 2022 at 9:39
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    Sometimes, set reviews will include a build time as well (depending on the reviewer), so looking for reviews can be a good place to start. But I suggest just getting a feel for how fast you build on average (in parts per hour eg.), and that'll give you a ball park number for any set (which you can then adjust for difficulty if needed). A rough guess could be around 10-20 seconds per part, or somewhere in the range of 200-400 parts per hour. Mar 13, 2022 at 15:52
  • @Alex, the set I had in mind was the recent ideas globe set, only having today in the afternoon time for it, I was wondering if I could build it in 1 sitting before having to start a busy work week. I totally miscalculated, didn't even finish half of it. Mar 13, 2022 at 20:06
  • @SanderDeDycker, I think your comment should be an answer instead. Mar 13, 2022 at 20:08
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    @MichaelVerschaeve : I haven't created an answer because I don't feel confident my experience can be translated to a general rule. It depends on too many factors. That said, finishing near half of a 2500 part set in an afternoon (assumed to be around 4 hours), is right in the middle of the rough estimated range I mentioned above. So at least you'll be better at estimating for future builds ! Mar 14, 2022 at 17:56

6 Answers 6


As others have said, there are probably too many factors to say how long a build will take. But, I thought it would be good to compile a list of factors that affect build time. Feel free to add to the list.

The Lego building process can be divided into two sub-processes; searching, and assembly.

Factors that affect searching time:

  • Number of parts in the pile (mixing numbered bags will increase searching time)
  • Experience of elements and colours
  • Any prior sorting of parts by size/colour (will have an overhead time cost, so only useful for large builds)
  • The distribution of parts (having many unique parts will take longer)
  • Eyesight and lighting
  • Determination
  • If the set is incomplete it can take considerable time to realise

Factors that affect assembly time:

  • Number of steps
  • Experience (both of the specific set and in general)
  • Building of symmetric/repeated sections in parallel
  • Build complexity
  • Dexterity and hand-eye coordination
  • Determination
  • Errors in Lego instructions (very occasional)

I am not sure it is possible to give specific guidance based on simple characteristics like part count or theme. In addition to the factors of the person (or people) undertaking the build raised in the comments, design also makes for wildly different building times.

For example, any set that has bilateral symmetry can be built comparitively quickly by building both sides at the same time even if they mirror each other. Sets that are not symmetrical will often take nearly twice as long. Another more obvious example is the use of advanced techniques that can sometimes make build time much longer, sometimes can drastically reduce complexity and build time, and sometimes have no effect.

Set type and part count do not take account of either those or similar factors like modularity and inclusion of large parts like BURPs or chassis. Labeled age range and part count can probably, at best, simply give a relative indication and no more.


I haven't checked how long it takes my 7 years old daughter based on number of pieces, but I saw she needs about 5 minutes per EUR of the set (with set prices in 20-50 EUR range; Friends mostly). This is for a new freshly opened set.

So, I would guess about 2 min/EUR for an adult that has built some sets but isn't a Lego fanatic. I haven't actually timed myself, though. So, I estimate a 10 EUR set would take about 20 minutes to build, a 100$ one would take slightly more than 3 hours etc.

Transferring these numbers to number of pieces per hour, at 10c/piece it gives ~300 pieces/hour. This sounds reasonable enough to me at first glance, but it is a fairly inaccurate method - though I believe all such estimation methods are.

Note this is only for assembly. Old large sets are slightly slower as all pieces are mixed together instead of being in bags, but it probably shouldn't slow you down too much. But if you need to find pieces with many sets mixed together, well, 10 sets is a problem, 100 is a nightmare. You should probably sort pieces first (by color, type or whatever else you prefer). And after sort you are still looking at a much longer build.


First you need to sort the pieces. So lets say you can sort 12 pieces per minute, then you later need to find them which is probably 6 pieces per minute and assemble them like 3 pieces per minute. So in total you need 7 minutes for 12 pieces. So in 4 hours you can do about 400 pieces.

It is a veeery rough estimate.

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    This is rough, very rough. This doesn't take in to account many things that reduce timing drastically. I know not everyone is as familiar with LEGO bricks as LEGO fans are, but 4 hours for 400 pieces set is way too much in most cases. School Day (60329) is just for the reference, to understand what ~400 piece modern set looks like. Another example is when you assemble big set, say Technic, you may be asked to put a lot of pieces in single step (116 pieces for set #42131, step 997), which doesn't take an hour to do.
    – Alex
    Mar 14, 2022 at 9:25
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    This answer does not consider that some people might not even sort the pieces before building, or do so only roughly.
    – zovits
    Mar 14, 2022 at 16:15
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    @Zovits, new sets I don't sort, they come in numbered bags which contain few enough different elements that the time spent sorting won't be compensated by the faster building imho. Second hand or older sets I definitely sort. Some people enjoy building in "hard mode" where they throw all bags from all steps together, I don't... Also, at whoever downvoted, the user shared his/her perspective/experience, he/she shouldn't be downvoted for that Mar 16, 2022 at 11:35

I would say I do about 300 to 500 pieces per hour.

  • Hi Klaus and welcome to Bricks.SE! Do you base your estimate on personal experience, calculations or other sources? Could you please elaborate?
    – zovits
    Mar 21, 2022 at 10:52

Its a correlation between number of parts + the set weight (to incorporate whether its many small pieces or rather few big pieces).

  • Hi MervX97 and welcome to Bricks.SE! Could you please elaborate on your answer? I mean it is not clear to me whether the weight you mention would positively or negatively correlate with either the piece size or the estimated building time.
    – zovits
    Mar 21, 2022 at 10:50

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