125 cubic inches ÷ 139 = 0.9, rounded up to 1 lb for UPS Daily Rates and FedEx. USPS bills actual weight because the box is not larger than 1 cubic foot.
How heavy does a 5x5x5 box need to be to avoid DIM charges?
With UPS and FedEx, anything packed under 1 lb is billed as 1 lb. Above that, you pay actual weight.