It doesn't look like 3b..Is your hair moisturized/styled in this picture?
I do think your hair could be anywhere from 3A to 3B.Here are some tips to make your curls pop so that it will be easier to tell what your curl pattern is. Wet it and load it up with conditioner until it won't soak up anymore conditioner. Apply a bit of gel, smoothing it through your curls. Gently scrunch and squeeze out excess moisture and product with an old t-shirt. Blow-dry on a cool setting with a diffuser attachment or air dry. You can also take the curl pattern quiz here: http://hairtype.naturallycurly.com/?#quizAnd take a look at this to learn more about 3A and 3B hair: http://www.naturallycurly.com/pages/hairtypes/type...More tips:About the Curly Girl Method: http://www.naturallycurly.com/curlreading/no-poo/t...About leave in conditioners: http://www.naturallycurly.com/curlreading/curl-pro...I hope that helps!
Remember, 3b curls are about sharpie width. Your hair looks like it has the potential to be 3b hair with a good hair routine. And don't forget, moisture is everything! Final verdict: 3a curls.
your hair looks like my hair when I've tied it up in a bun and simply neglected due to rotational shift work also my hair looked just like that before I had a snip due to colour damage I think you maybe a 3b up load a pic after you have washed and left moisture in it because the pic looks like damaged curly hair