DN ( dhexroorka magaca ah) waxaa loola jeedaa dhexroorka magaca ah ee tuubada, taas oo ah celceliska dhexroorka dibadda iyo dhexroorka gudaha. Qiimaha DN = qiimaha De -0.5*qiimaha dhumucda gidaarka tuubada. Fiiro gaar ah: Tani maaha dhexroorka dibadda ama dhexroorka gudaha.

Biyaha, tuubooyinka birta gudbinta gaaska (tuubada birta galvanized ama birta aan galvanized), tuubada birta tuuray, birta-caag tuubo isku dhafan iyo tuubooyinka polyvinyl chloride (PVC), iwm, waa in lagu calaamadiyaa dhexroor magac ahaan "DN" (sida DN15, DN50).

De (dhexroorka dibadda) waxaa loola jeedaa dhexroorka dibadda ee tuubada, PPR, PE pipe, dhexroorka dibadda ee tuubada polypropylene, guud ahaan lagu calaamadeeyay De, oo dhan waxay u baahan yihiin in lagu calaamadiyo qaabka dhexroorka dibadda * dhumucda derbiga, tusaale ahaan De25 × 3.

D guud ahaan waxaa loola jeedaa dhexroorka gudaha ee tuubada.

d guud ahaan waxa loola jeedaa dhexroorka gudaha ee tuubada shubka ah. Tuubooyinka shubka ah ee la xoojiyay, tuubooyinka dhoobada ah, tuubooyinka dhoobada ah ee u adkaysta aashitada, dhoobada dhoobada iyo tuubooyinka kale, kuwaas oo dhexroorka tuubada ay tahay in lagu matalo dhexroorka gudaha d (sida d230, d380, iwm.)

Φ waxay u taagan tahay dhexroorka goobada guud; waxay sidoo kale matali kartaa dhexroorka dibadda ee tuubada, laakiin markan waa in lagu dhufto dhumucda derbiga.