Inkqubo yamazwe ngamazwe yeeyunithi zokulinganisa

I-International System of Units, i-SI efinyeziweyo (ebizwa ngokuba yi-esse-i  ), yeyona nkqubo ixhaphake kakhulu yeeyunithi .I- Convention ye-Meter ye-1875 yabeka iziseko zenkqubo eqhelekileyo yeeyunithi zokulinganisa, ezibizwa ukususela kwi-1961 i-International System . Ekuhambeni kwexesha, ezinye iiyunithi ezisisiseko zokulinganisa zongezwa, zafikelela kwisixhenxe ngowe-1971; nganye kuzo ibhekisela kubungakanani bomzimba . Zonke ezinye iiyunithi zokulinganisa zisuka kwezi kwaye ke zibizwa ngokuba ziiyunithi ezithathwe. 

Amanye amazwe ase-Anglo-Saxon, nangona eyamnkele inkqubo ye-SI, asasebenzisa iiyunithi eziqhelekileyo, njenge-US kunye ne- Bhritane .Ubunzima benkcubeko yotshintsho ukusuka kwenye inkqubo ukuya kwenye bunxulunyaniswa ngokusisiseko neengcambu zembali. Inkqubo yamazwe ngamazwe isebenzisa iiyunithi zesistim yemetriki ezalelwe kumxholo weNguqulelo yesiFrentshi : Iiyunithi ze-SI zinamagama afanayo kunye nobukhulu obusebenzayo obufana neeyunithi zemetriki. Inkqubo, esekwe kubungakanani bexesha lobude bobunzima, yaqala yabizwa ngokuba yiNkqubo yeMKS ukuyahlula kwiNkqubo yeCGS efanayo; iiyunithi zayo zokulinganisa yayiyimitha, ikhilogram neyesibini endaweni yesentimitha, igram, yesibini.