Isar da daidaitaccen tsayincarbon karfe bututu, wanda kuma aka sani da tsayin buƙatun mai amfani ko tsawon kwangilar, akwai tanadi guda huɗu a cikin ƙa'idodin da ake dasu:

A, Tsawon al'ada (wanda kuma aka sani da tsayin da ba bazuwar): kowane tsayi tsakanin tsayin ma'aunin da ake buƙata kuma babu tsayayyen buƙatun tsayin da ake kira tsayin al'ada.

B, Tsawon yanke: tsayin yanke ya kamata ya kasance a cikin kewayon tsayin da aka saba, wanda ake buƙata a cikin kwangilar ƙayyadadden tsayin tsayi.Amma ainihin aikin yana da tabbas yanke kuma ba shi yiwuwa, don haka ma'auni ya ƙayyade tsawon tsawon tsayin daka mai kyau da aka yarda.Samar da raguwar tsayi fiye da tsayin bututun bututu yawanci shine yawan amfanin ƙasa babban rata, masu kera suka gabatar da ƙarin farashin farashi ya dace.Kamfanonin Markups ba su da daidaito, yawanci suna dogara ne akan karuwar farashin tushe na kusan 10%.

C, Tsawon Biyu: bisa ga buƙatun tsari, tsayin shine madaidaicin lamba kuma ana magana da shi azaman tsayi biyu.Tsawon ninki biyu ya kamata ya kasance a cikin kewayon tsayin da aka saba, kwangilar ya kamata ya ƙayyade tsayin tsayi guda biyu da abun da ke ciki na jimlar tsayin tsayi.A aikace, jimlar tsayin ya kamata ya dogara ne akan madaidaiciyar madaidaicin yarda tare da 20mm, tare da tsayin ninki biyu na kowane gefe guda ɗaya yakamata ya kasance.Idan ma'auni ba daidai ba ne tsawon ninki biyu da buƙatun yankan gefe, ya kamata a yi shawarwari da bangarorin biyu kuma a ƙayyade a cikin kwangilar.Lokutan tsayin tsayin ma'auni daidai da abin da ake samarwa zai kawo raguwa mai yawa a cikin yawan amfanin ƙasa, don haka masu samarwa suka ba da shawarar haɓaka mai ma'ana, kuma ƙimar haɓakarsa tare da tsayin ƙimar haɓaka daidai tsayi iri ɗaya.

D, Tsawon iyaka: tsayin kewayon yana tsakanin kewayon tsayi na al'ada, lokacin da mai amfani ya buƙaci ƙayyadadden kewayon wanda tsawon lokaci, ana buƙatar bayyana su a cikin kwangilar.