A crochet oval grows around both sides of a starting chain. The middle of that chain creates two straight sections, while increases at its ends create the curves. Once those areas are marked, the oval is easier to control than a long list of stitches makes it appear.
Stitch terminology: This guide uses US names. US single crochet is UK double crochet; US half double is UK half treble; US double is UK treble. See the full US/UK reference.
Understand what the starting chain controls
A longer starting chain gives a longer straight middle section. Adding rounds increases the width and length around it. That means an oval with the right width but too little length may need a different starting chain, not simply more rounds everywhere.
Make a small sample before planning a bag base. The final dimensions depend on the stitch gauge and the increase method.
Work a small first round
For this single-crochet exercise, chain eight. Single crochet in the second chain and in the next five chains. Work three single crochets in the final chain. Continue around the underside of the chain, making one single crochet in each of the next five available chain positions, then two in the first chain position where you began.
You have sixteen stitches. The initial single crochet and the final two form one three-stitch curved end; the three stitches in the far chain form the other. Between them are two straight sections of five stitches.
Mark all six curved-end stitches
Use one marker colour for the straight-side boundaries and another for the round start. In the second round, work two single crochets in each of the six curved-end stitches and one in each of the ten straight-side stitches.
That produces twenty-two stitches: sixteen plus six increases. Work continuously for this exercise, moving the round-start marker, rather than counting a joining slip stitch as another stitch.
Grow the curves without widening the straight sections
In a common six-increase oval method, later rounds add three stitches around each curved end while the number of straight-side stitches stays constant. The increases become more widely spaced as each curve grows.
The exact spacing and round-start position depend on the pattern. Follow a complete method, such as the credited demonstration, rather than combining its increase formula with a different starting orientation.
Check the two ends against each other
If one end looks larger, count its stitches between the side markers. It is easy to forget that the starting end was split between the beginning and end of round one. Treating only the final two stitches as that whole curve would miss the initial single crochet.
If the entire oval cups or ruffles, check the count first, then assess whether the increase rate suits the actual yarn and stitch height.
Measure before turning the base into sides
Lay the oval flat and measure both length and width without stretching it. For a bag, confirm that the base suits the objects you want to carry and the planned side construction. A back-loop transition can create a visual edge, but it does not correct an incorrectly sized base.
Keep the chain length, round counts and finished measurements together. Those notes let you change the long axis and the width deliberately on the next sample.
Continue learning
Compare circular growth · Plan a bag base · Track rounds and markers
Browse the crochet learning library.