Girman jujjuyawar maganadisu, wanda kuma aka sani da ƙarfin filin maganadisu ko kuma filin maganadisu kawai, an ayyana shi azaman adadin ƙarfin maganadisu da ke wucewa ta ɓangaren yanki na abu. Ana auna shi a cikin raka'a na tesla (T) ko gauss (G), kuma ana nuna shi da alamar B. A lissafi, ana ba da ƙimar ƙarfin maganadisu ta hanyar dabara B = μ₀H, inda μ₀ shine ikon sararin samaniya kuma H shine ƙarfin filin maganadisu. Girman juzu'i na Magnetic shine babban mahimmanci a cikin electromagnetism kuma ana amfani dashi a aikace-aikace da yawa, gami da levitation na maganadisu, injin MRI, da injin lantarki.