Kell Brook has weighed in at 156.9lbs for his IBF world title fight with Errol Spence, who was 155.8lbs on the check weigh-ins.
Both fighters are only allowed to put on 10lbs between Friday's weigh-in and Saturday's check call.
Brook returns to the welterweight division since gaining 13lbs for his most recent fight - a fifth-round stoppage at the hands of middleweight king Gennady Golovkin in September.
"You can imagine I'm a big guy so it's been very difficult but I've stuck to the plan, absolutely 100 per cent," Brook said.
"I've been monitored all the way and I feel very good now."
The American challenger tipped the scales at around 8am and was happy with the number he posted ahead of Saturday night's bout at Bramall Lane, live on Sky Sports Box Office.
"I feel strong, happy," Spence Jr said. "I've eaten, I've fuelled up. I've been down at 147 for a while now so my body has adjusted to it.
"Ten pounds is good for me; I won't feel sluggish and I'm still fast and strong.
"I know that my time is tonight and I won't waste any energy today, I'll stay cool. I don't let anything get under my skin and I won't be distracted from my game plan tonight."
