"以内宽计算" can be translated into English as "calculated based on the inner width" or "measured and calculated within the inner width", depending on the specific context and intended meaning.
If you're emphasizing that a measurement or calculation is done considering only the inner width (excluding any additional margins or thicknesses), "calculated based on the inner width" would be appropriate.
If you want to convey that the measurement or calculation is confined to or occurs within the limits of the inner width, "measured and calculated within the inner width" could be used.
In many technical or engineering contexts, a more precise and specific term might be used based on the industry or field's conventions.