Loft yog ib qho tseem ceeb thoob ntiaj teb qhia rau ntsuas qhov sov so ntawm down, xa mus rau lub ntim nyob rau hauv cubic inches nyob los ntawm ib ooj (30 grams) ntawm down nyob rau hauv tej yam kev mob. Piv txwv li, yog hais tias ib ooj ntawm down occupies 600 cubic inches, nws loft yog hais tias yog 600. Feem ntau hais lus, plump, mature noog muaj dua loft, thaum me noog muaj qis loft.
Tab sis dab tsi yog kev siv loft? Ib qho kev piav qhia yog qhov sau lub zog sawv cev rau "quantity" ntawm down, thaum cov ntsiab lus down txiav txim siab "zoo," nrog loft yog ib qho tseem ceeb qhia. Nrog tib lub zog sau, ib lub tsev siab dua qhia tias muaj kev sov siab dua. Qhov no yog vim hais tias siab dua loft txhais tau hais tias ntau insulating huab cua nyob rau hauv lub down, ua rau cov rwb thaiv tsev zoo dua.