The 15mm Rule Of Fun

Last night I was pressing a 15mm (5/8″)* fold into a piece of fabric. At least, I think the fold was 15mm (5/8″) deep – I was eyeballing it. Because, you know, dragging my behind across the room for a tape measure was not an option.

Hmmm, I thought. How can I be so sure of my 15mm? And could others be sure, too?

Time for a little game! Below are four pieces of fabric. One of them is pressed over by 15mm. The other three are pressed over by incrementally different widths. Which of the four options do you think is the 15mm (5/8″) fold? Leave a comment and see if you can eyeball 15mm! Now, shush with your protestations that computer screens distort pictures. It’s just a bit of fun, innit? I’ll let you know if you were right, all in the fullness of time.

Rock and roll, my friends, rock and roll.

*For beginner Sewists, 15mm (5/8″) is a fairly standard seam allowance or commonly used measurement in dressmaking. You’ll often find a groove on the throat plate of a sewing machine that is 15mm (5/8″) away from the needle.

Seam Allowances

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148 Responses to The 15mm Rule Of Fun

  1. shivani says:

    3? I do this all the time (and then pout when things don’t work out).

  2. raquel from florida says:

    It looks to me the the 15 mm rule and the 5/8 inch rule have the same problems….heheheh. I guess is number 3

  3. Matte says:

    I’m torn between 2 and 4, but thinking maybe 4?

  4. Julia says:

    I say 2?

  5. Tamsin says:

    Hmm, I think number 2. I often guess-timate that kind measurement too.

  6. Jessi says:

    No idea! I don’t do garments enough to eyeball it, but if you wanted a quarter inch quilting seam- that I can do!

    I think it is 3, because 15 mm is a bit larger than half an inch.

  7. Debbie Cook says:

    3? But I don’t think in metric so I’m hoping 15mm = 5/8″?

  8. Jenny says:

    hmmm, I’m going to guess #2
    hehe I usually eyeball it too! especially when I sew with knits – who cares? they stretch! I’m much more careful when I’m sewing with non-stretch.

  9. Debi says:

    I vote for number 1. numbers 2 and 4 look the same to me….

  10. JacqC says:

    I’m breaking out in a sweat – I am totally incapable of eyeballing a measurement, I would have to use a tape measure (probably twice!). I can’t even guess! Off for a lie down 😉

  11. France Parijs (alias) says:

    I would say number 1 🙂

  12. Reethi says:

    I have no idea, but if it’s a hem or something I need to do, rather than drag out a tape measure mark off and pin in place, I’ll just baste myself a row of stitches to serve as a guide. A lot faster!

  13. Janice A. says:

    3 !


  14. jenny says:

    I’m going with 3, only because I’m often surprised at how wide it actually is!

  15. Wanda says:

    I say 1

  16. Charlie says:

    I’m going for 4, or may be 2…no 4. Definitely 4. Possibly.

  17. Andrea says:

    I’m going with number 1

  18. I sew more vintage patterns that use 1/2″ so it took me a second to realize 15mm was 5/8″. lol I’m going to vote #4.

  19. Pat beadle says:


  20. Fiona says:

    I think it’s 1.

  21. Melizza says:

    I’m going with 4.

  22. Marie says:

    I was totally going with #2, but then I looked closer and panicked and now I’m totally going with #3! I’ll find it totally hilarious if it’s neither of course ;o) By the way…is that the fabric you took off me at the Walthamstow swap that you also made pyjama bottoms with? If so…it’s never ending ;o)

  23. KC says:

    Number 1. No idea why I think that.

  24. Laura says:

    There’s no way to tell scale in the picture except for the pins and those could be smaller or bigger, but to my eye #2 looks closest to 5/8″. I definitely do this myself when sewing – eyeball hems and seams and I’m usually pretty on. I can see a 1/4″ seam for quilting fairly well too. Once you’ve done it for a while you get a feel for it, although obviously I still use my seam guide or measure when it’s super-key to get right, with multiple match points etc.

  25. I say number 2, but when I started to sew we used feet and inches so it can be all very much hit and miss with me. But hey who cares.

  26. CGCouture says:

    My guess is #1. I do the eyeball thing on hems “in the round”, but a lot of times I make a few marks and then kind of eyeball it to match where there are no marks.

  27. houseofpinheiro says:

    LOL, I use my index finger and works every time… my guess based on the photo is number 1?

  28. black label says:

    im also going with 1!

  29. I agree there’s no way to tell scale here really. But I do think it’s interesting how you can learn to see a certain measurement with a fair amount of accuracy! I use 1/2″ seam allowances a lot and I find I can turn up that much by eye and be remarkably close, although I do usually use the ruler to check at least the first few points.

  30. Zuzuni says:

    I believe it’s number 3. A standard pin is about 30 mm and that fold looks like it’s “half a pin”.

  31. Sue says:

    I think it is number 3! Tricky!!!

  32. Kat H says:

    I’m guessing number 3. And I’m fairly sure number 1 is a 1cm seam allowance. (When I first took up sewing again, years ago, it was via a basic pattern-drafting class and the teacher advocated a 1cm seam allowance, which I then used for years. So I’m a lot better at eyeballing a 1cm allowance than a 1.5cm allowance.) (And after saying that, I’ve probably guessed completely incorrectly that #1 is 1cm!)

  33. christina says:

    My guess is #2. This is fun!

  34. I’m guessing number 4

  35. Erin Cumming says:

    I’m going to trust my mild case of OCD and choose #2.

  36. Lisette says:

    I’m guessing 4 but the different lengths and widths of the panels themselves AND a print, as well as having no idea what width any of the panels are to begin with? Totally guessing.

  37. Carolyn says:

    I’ll play – #3

  38. Catherine says:

    I machine a line of tacking / long stitches on the 1.5cm lines – acts like perforations on a bill and helps the fabric fold at the point you want it too…

  39. I vote for number 3 please 🙂

  40. Ella says:

    Have to go with 2, tricky….

  41. My instinct says 4, but whenever I eyeball something and then measure it, it’s generally a little bit too big, so chances of me being right are slim…!
    And assuming you’re not being tricksy and using extra long quilters’ pins to mess with us…?! 😉

  42. MrsAlex says:

    Ermmm, 2?

  43. Alex in California says:

    I think it is sample 3.

  44. Jacqueline says:

    I’m guessing number 3, but since I’m not that accurate with my seams, I’m not sure

  45. I’m thinking 2…and that I’ll never not measure a seam allowance ever again! 😉

  46. Jen (NY) says:

    I’m judging by the center portion of each, since the pinned portion distorts the fabric. I’ll say sample #4 is the 5/8″ fold.

  47. MarcyF says:

    No. 4!

  48. Elle C says:

    I think it’s #1, but even now I am second guessing myself.

  49. Emilie says:

    It’s either 2 or 4… they look very similar, but if I have to go with only one of them, I guess 2.

  50. Funnygrrl says:

    I mean four.

  51. Claire S. says:

    hmmm – 3 ? but every time I look, I want to change my mind LOL

  52. pat says:

    I would say 2.

  53. Sara says:

    SA number 2 is 5/8. That’s my guess.

  54. Nic says:

    I think it’s 2. I never measure hems. works out – most of the time!

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  56. Alessa says:

    I’d also go with #2.

  57. kaitui_kiwi says:

    I’m going for number four…I think the print on a fabric can really throw your eye off so some fabrics make it easier to gauge the S/A and some make it much harder. I usually get my 15mm started with a measure then eyeball for a bit, then re-check to see how badly I’ve shifted either way…haha, I guess I am more careful when it matters.

  58. Kieran says:

    I’m guessing 1!

  59. 5currantbuns says:

    I’m ok eyballing 10mm as that’s the width of my finger pretty much…15mm a bit more difficult..but I’d say 4, I think 1 may be 1.25 as it looks slightly more than my finger width…

  60. missparayim says:

    I am waffling between 2 and 4, but I think it’s 4.

  61. Jacinta says:

    I say #2!! Oh the suspense is killing me! 😛

  62. liza jane says:

    You know what’s funny– I was just tooting my own horn about this. My husband was giving me a hard time because I was explaining how awesome I was the other day while making curtains. My 1/2 hems were eyeballed and were perfect! He likes to bring me back down to earth though. I’m going to say 1.

  63. Sewer from across the Pod. says:

    1? I try to use only 1, 1/2 and 1/4 seam allowances because 5/8 is too hard to measure.

  64. Sewer from across the Pod. says:

    BTW, I never, ever eyeball. I’m not consistent.

  65. Lyndsay says:

    I tried to use the pins for help too :-s I think 4?

  66. Claire says:

    4! I’m also getting to the point where I’m too lazy to measure silly seam allowances.

  67. Phyllis says:

    I think it’s #4. I always eyeball hems and such!

  68. creative pixie says:

    Is it no.2

  69. I think 2! Though 4 looks the same to me!

  70. Joy says:

    I think number 4!

  71. Shelly says:

    I’m torn between 2 and 4 but I think it’s 4!

  72. sewexhausted says:

    I am going to make a wager on #2… And then put tape measures in all the places I work so I never eyeball again! 😉

  73. Nina says:

    I’m guessing #4. without a penny or small article for scale, it’s hard to tell.

  74. I’m guessing #3, mostly related to how that looks against my mental tape measure, which is probably wrong. There are marks on my machine to indicate varying widths, so while I do eyeball quite a bit, it’s not quite as free and easy as it sounds. I fold and align against whichever of the marks meets the size I’m supposed to be sewing (or I decide will do the job). 😉

  75. Karen says:

    WHAT??? 15 mm??? Here across the pond, I could never, ever guess about a metric measurement, but #2 looks like 5/8″ to me. I eyeball this one a lot, too!

  76. Sufiya says:

    Actually I find that I am excellent at “eyeballing”; it’s just a matter of practice! There are jewelers in India who never use scales; they weigh gems in the palm of their hands and make no mistakes when tested against an They train from an early age; the wife of one such man says he can go to the market and never use a scale to weigh anything, and he is always dead on!

    Unfortunately here, the pics are not to scale, and so it’s difficult to tell exactly which would be the 5/8 seam, but if I had to guess, it’s a bit of a tossup between 2 and 4. If pressed real hard, I’d have to go with #2!

  77. Sufiya says:

    …that should read: “…and make no mistakes when tested against actual scales!” Proofreading BEFORE submitting is always good!

  78. Liz says:

    I vote #2. BTW – this totally kept me wearing a size 16 for years when I was bigger. Just sew smaller seams!! Who was I kidding?!

  79. Stephanie says:

    This would be easier if it were in front of my eyes as pins vary in size and there is no other point of reference- plus how far away your camera and the zoom factor you used in relation to the fabric is a factor as well. But I’m enjoying everyone’s guesses. I know if I could if I had the fabric in front of me though!

  80. EmSewCrazy says:

    Very tricky to leave scale out! My gut says it is number 1.

  81. Phil says:

    Erm I think 1 or 2. The others are surely too wide? I don’t eyeball unless using the guide on my machine (I’m sure that doesn’t count!). too insecure (sob!)!

  82. KathleenS says:

    From here it looks like number 1, but I would have more confidence in my ability to tell if I saw it in real life.

  83. Heather says:

    Is it no. 3, although my seams are more like no. 1, yikes!

  84. Paola says:

    I’m guessing No 2

  85. Nikki says:

    I’m going for number one, I do sometimes eyeball my hem allowance, then double check it with the tape measure!

  86. Sam says:

    2 and 4 are my top picks – and I’m committing to 2.

    It’s an interesting and simple exercise that I’m going to make up for a lass I’m teaching to sew (we start tomorrow – how timely of you, Karen!).


  87. I’m guessing that it is no. 2

  88. lientje says:

    My guess is #4. What a fun game 😀

  89. ZoSews says:

    I’d guess 2 or 4… I’ll go with 4 though 🙂

  90. Robyn says:

    I’m a ‘finger measurer’ too – so I’m saying number 1.

  91. teacupchild says:

    Going with 4! Ughhh it is going to bother me all night, haha!

  92. LizLusaka says:

    Number 1! When I can be bothered, I cut a bit of cardboard of 1.5cm and use that as a guide….

  93. Teresa says:

    I believe it is #2.

  94. Karen in VA says:

    I’m guessing #1 as when I try to eyeball that length I always go too big…

  95. EJ says:

    I’m going for 1… but interested to know as a beginner sewer.

  96. ecochic87 says:

    I’m going to say 4!

  97. 1 looks more like 1/2 inch, and 2 looks closest to my eyeball 5/8″. 4 runs a close second.

  98. LinB says:

    I guess #2. A handy always-on-your-body measuring device (well, for most people it’s always on your body) is your hand and fingers. Most people’s first knuckle on their index finger is about one inch long. Many, many knuckles are about 5/8″ across. Hands are about eight inches from bottom of palm to tip of longest finger. Even if your own personal measurements are a bit off one way or the other, your fingers and hands are an excellent way to estimate distance when precise measurements are not critical (and for most garments, you’re okay to be 1/16″ off here and there, since fabric is largely a fluid medium).

  99. Louise says:

    I’m guessing 4.

  100. Louisa says:

    I’m pretty accurate at 5/8″ seams without a ruler but you didn’t give us anything to judge by, you sneak! I’m waffling between 2 and 4….OK, #4.

  101. Regina says:

    I believe it is #3.

  102. Kelly says:

    I choose # 2; it looks about right to me.

  103. Sheree says:

    I haven’t looked at any comments – will read them all after this. To me, it stands out as being 3 ???

  104. Becky says:

    #3, I usually do not measure this, and I am usually very close. Can’t wait to see the answer.

  105. gillymakes says:

    Number 4 for me, I think.

  106. Galica says:

    In analogue, I usually eyeball. In digital, it’s a little harder! But I think it’s no. 2. (Also, like the fabric. Hmmmm florals)

  107. Susan says:

    I was torn between 2 and 4, but I’ll stick with my 1

  108. Shirley says:

    I think it is # 1. I just recently found all the sewing blogs and I have really enjoyed them. I find you to be knowledgeable, entertaining and your work is so well done.

  109. Molly-Made says:

    I’m gonna say 3? I never measure anything (entirely out of laziness of course) from baking to sewing and count my lucky stars when things work out. I live in a world governed by luck 🙂

  110. ramonabags says:

    I think it is number 1

  111. DonnaB says:

    My Vote goes to number 2!

  112. I am thinking 2, but I have made myself a paper template for ironing these things 🙂

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  114. angela says:

    I instantly thought #2 when I looked at the four examples! Was glad to see that several others thought the same thing as I scrolled through the comments 😉

  115. Clover says:

    4! She says with confidence… Mmm or maybe not. And that’s why things don’t quite fit. Quite often!

  116. Sarah says:

    Number 4

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