A 9×13 inch pan typically yields 24 standard bars (cut 4 rows × 6 columns), 20 medium bars (4×5), or 16 generous bars (4×4). For parties, 24 bars is the standard — each is a good two-bite portion. For potlucks, 16 larger bars travel more reliably without falling apart. Score the top lightly with a knife before fully cutting to ensure even sizing.

Yes, but reduce oven temperature by 25°F and add 5–10 minutes to the bake time. Glass conducts heat more slowly and less evenly than metal. Metal pans (especially light-coloured aluminium) give the best results for bars — darker metal pans can over-brown the bottom crust. If using glass, check for doneness by the visual cues in each recipe rather than strictly following the time.

Three key steps: (1) Always chill completely before cutting — at least 1–2 hours in the refrigerator. (2) Use a sharp chef’s knife run under hot water, dried, and cut in a single downward motion without dragging. (3) Clean and re-warm the blade between every cut. Wiping the blade between cuts removes crumbs and filling that cause drag and smear the edges of subsequent cuts.

For outdoor summer events, prioritise bars that don’t require refrigeration and won’t melt or become sticky in heat: brownies, pecan bars, honey almond bars, crumble bars, and s’mores bars all travel well in warm weather. Avoid cheesecake bars, lemon bars, and any bars with cream cheese frosting for outdoor events unless you have a cooler. Keep all bars in the shade and consume within 2 hours if the temperature is above 75°F.

Yes — use two 9×13 pans rather than one deeper pan. A doubled recipe in a single deep pan won’t bake evenly — the centre will be underdone long after the edges are overcooked. Two pans at the same temperature and time work perfectly. Rotate pans at the halfway mark for even baking. Both pans on the same oven rack (if it fits) or different racks with rotation both work.