Gauge, What would you do

I am making the Debbie Bliss ballet top for my daughter.

I have done my swatch and I am not matching gauge. I am getting 27 stitches and 36 rows to 4 inches. the pattern calls for 25 and 34 rows on size 3 needles. Should I go up one or two needles sizes for my next swatch?

I haven’t washed and blocked my swatch yet and will do that first, but I still think I will be off.

have you bound off the swatch? if not go up one needle size and carry on knitting for a few rows, then change to a bigger size again and do another few rows before binding off. that way you can directly compare the gauge and fabric before asnd after washing and blooking

Think about it this way: measure how wide the 25 st are on your swatch. Are they 3.75"? About 1/4" too narrow for every 25 st?
Then multiply that error across the entire width of stitches for all the body pieces. It is staggering how just 2 st off in gauge can make a garment either way too small, or way too big, in the end results.

Keep trying to get the correct gauge with a different needle size, except that I always just start a new swatch.

FYI: sometimes a real tight (or a real loose) cast-on row can affect the resulting gauge immediately above the cast on row. You could try your new swatch with a looser cast-on and use the same needles. Are you knitting a full 4" in length swatch? This also helps reveal the true gauge.

Swatching is a chore, to be sure…but incorrect gauge can destroy the ‘fit’ of a garment. Been there, done that!

You should actually CO 30-35 sts for the swatch so you can measure the 4" over the center sts. The edge stitches may not be the same size, or they curl under, so you can’t get as accurate a measure. Also, many patterns assume that you wash and/or block the swatch the way the finished item will be. And maybe that’s how they all come up with the gauge they do.

This will be my first sweater so I want it to be right. I made a 6" by 6" swatch and counted in several places. I bound it off and have washed and blocked it. It should be dry in the morning to count again. With the difference in what I got and what I need which needle size would you try next?

Alrighty… you did everything correctly. So… go up one needle size to start, but you may need to also do as tarentella suggests - work about 3" in the next size, then do a purl row on the knit side (or knit the WS row) and work on the next size up from that all on the same swatch. Then you should be able to tell which will be correct.