jQueryで要素の間隔を取得する方法を示すスニペットがあります。
/* messing vertical spaces of block level elements with jQuery in pixels */
console.clear();
var jObj = $('selector');
for(var i = 0, l = jObj.length; i < l; i++) {
//jObj.eq(i).css('display', 'block');
console.log('jQuery object:', jObj.eq(i));
console.log('plain element:', jObj[i]);
console.log('without spacings - jObj.eq(i).height(): ', jObj.eq(i).height());
console.log('with padding - jObj[i].clientHeight: ', jObj[i].clientHeight);
console.log('with padding and border - jObj.eq(i).outerHeight(): ', jObj.eq(i).outerHeight());
console.log('with padding, border and margin - jObj.eq(i).outerHeight(true):', jObj.eq(i).outerHeight(true));
console.log('total vertical spacing: ', jObj.eq(i).outerHeight(true) - jObj.eq(i).height());
}