No, kilt sizes are not the same as trouser sizes. Kilts are worn higher on the body — around the natural waist, near the navel — which is usually a few inches larger than the waistline used for trousers. For example, if you wear a 34-inch waist in trousers, your kilt waist size might be closer to 36 or 37 inches.
Always measure your actual body, not your clothing size, when ordering a kilt to ensure the correct fit.