Mecha Freeza: 94,500,000
-- Full Power: 135,000,00
King Cold: 95,000,000
Freeza was walking around suppressed, Gohan says that Freeza can still become much more powerful and it was never noted that he increased his power after he lands on Earth. I imagine he was walking around with 70% of his power because, on Namek, that’s the most we’ve seen him capable of without needing a lot of time to power-up. He said that he could beat Goku, but how could he know? He just has credibility when it comes to knowing how strong he is, not others, so I don't think he increased his power too much. Cold was stated to be around the same dimension as a suppressed Freeza, so he's weaker than full power regardless (unless he was suppressed too, but after seeing his son getting sliced, I imagine he would use his full power, but no character noticed a power increase).
Future Trunks: 3,000,000
-- Super Saiyan: 150,000,000
Son Goku: 3,400,000
-- Super Saiyan: 170,000,000
Gohan said that, in Super Saiyan, Trunks had the same Ki as his dad. Could be referring to SS itself, but I see no problem in having Trunks with this battle power, personally. Goku possibly spent some time training, but more-so focused on learning Instant Transmission. His Super Saiyan strength is enough to be stronger than Trunks, but Goku also said that Trunks wasn't completely serious, so Goku doesn't have to be necessarily a lot stronger than Trunks.
Vegeta: 2,500,000
Piccolo: 2,600,000
Piccolo is confident on taking on Vegeta and Goku, when he arrives, asks Piccolo first if he was the one who defeated Freeza. Small and irrelevant difference either way.
Son Gohan: 1,000,000
Kuririn: 450,000
Tenshinhan: 400,000
Yamcha: 340,000
Chaozu: 230,000
I have trouble believing that the humans could increase their power so much, but stranger things have happened in the series. I increased Piccolo's power a lot before he fused with Nail, so why not increase the humans a lot too?
3 years later: ---------------------------------
Son Goku: 3,500,000
-- Super Saiyan: 175,000,000 and decreasing
-- post-Kamehameha: 110,000,000 and decreasing
Vegeta: 4,500,000
-- Super Saiyan: 225,000,000
----- Tired: 65,000,000
Goku is, obviously, sick and so he's not demonstrating his full power in this fight, with his Ki constantly decreasing. Tenshinhan is surprised once Goku turns Super Saiyan, implying Goku's stronger than 3 years ago but Piccolo knows he's weaker than he should be. Vegeta's stronger than Goku even if he weren't sick. Piccolo implies Vegeta would have lost to #20, which makes sense considering not only did he get a large chunk of his Ki sucked off, but he also fired off a Big Bang Attack to finish off #19.
Artificial Human #19: 70,000,000
-- post-Kamehameha: 135,000,000
-- after absorbing Ki from Goku and Vegeta: 170,000,000
Artificial Human #20: 72,000,000
-- after absorbing Vegeta’s Ki: 80,000,000
-- after absorbing Piccolo’s Ki: 120,000,000
It's somewhat far-fetched to think they'd be stronger than Freeza from the get-go, plus later Kuririn asks Goku if he's ready to fight someone stronger than Freeza and that's only after #17, #18 and Cell come into the picture. I think they only surpassed Freeza the moment they started absorbing Goku, Vegeta and Piccolo's Ki. Gero is stronger than #19, because I don't know why he'd build #19 stronger than him; they could be equal though.
Piccolo: 12,000,000
-- Full Power: 120,000,000
----- No weights: 150,000,000
Piccolo was suppressed when Goku was fighting #19, hence why he got knocked down by Gero, of course. I don't think he would be so eager to fight the androids if he didn't at least surpass Mecha Freeza's suppressed power on Earth. It's debatable on whether or not he surpassed the Super Saiyans, but I reckon it really doesn't matter at all.
Future Trunks: 4,350,000
-- Super Saiyan: 217,500,000
Kuririn: 490,000
Yamcha: 370,000
Tenshinhan: 420,000
The humans should have trained a bit.
Fight with Cell: ---------------------------------
Piccolo, post-fusion: 280,000,000
-- No weights: 350,000,000
Artificial Human #18: 345,000,000
Artificial Human #17: 350,000,000
Artificial Human #16: 440,000,000
Imperfect Cell: 275,000,000
-- After absorbing humans: 440,000,000
This is where the battle powers start getting absolutely ridiculous. Imperfect Cell is at the very least stronger than a Super Saiyan since he killed Trunks, but he's weaker than the androids. He was shown to be weaker than Piccolo with weighted clothing, which means the androids are at least 1.25x stronger than Cell. After absorbing humans, Cell completely destroys #17 and Piccolo, meaning the gap should be around 25%.
Tenshinhan: 420,000
-- Shin Kikoho: 42,000,000
Each Kikoho has a battle power of 42 million, enough to slow down Cell, but not enough to actually do some damage.
Vegeta: 10,700,000
-- Super Saiyan: 535,000,000
-- Grade 2: 749,000,000
----- Final Flash: 1,040,000,000
Future Trunks: 10,600,000
-- Super Saiyan: 530,000,000
-- Grade 2: 742,000,000
-- Grade 3: 1,060,000,000
Semi-Perfect Cell: 550,000,000
-- Full Power: 685,000,000
Perfect Cell: 935,000,000
Once Imperfect Cell absorbed #17, he destroyed #16 completely, meaning there has to be another large gap between the two of them. He can increase his power even further, as demonstrated in his fight against Vegeta, and yet is incapable of hurting the Saiyan. Trunks says "already?" when Vegeta uses Grade 2, implying Super Saiyan is at least stronger than the androids at this point. Grade 3 is a whopping one hundred times multiplier because there's a huge gap between Perfect Cell and Grade 2 Vegeta, just as there's a somewhat huge gap between Grade 3 Trunks and Perfect Cell.
Cell Games: ---------------------------------
Mr. Satan: 7
Son Goku: 50,000,000
-- Super Saiyan, 50%: 1,250,000,000
-- Super Saiyan: 2,500,000,000
Goku's 50% power surprised both Trunks and Vegeta immensely when he showed it off to Karin, implying he was massively stronger than both of them at their best.
Gohan: 60,000,000
-- Super Saiyan: 3,000,000,000
-- Super Saiyan 2: 6,000,000,000
----- Super Saiyan 2 with one arm: 3,000,000,000
----- Rage boost: 7,500,000,000
Gohan was, of course, a lot stronger than anyone else. He says his Ki dropped by half and Cell was playing around with him in the Kamehameha struggle, so I don't doubt his words, considering half his power still makes him stronger than anyone else. The Daizenshuu says Gohan had his power boosted by rage in this fight, and considering Cell not only got his equivalent to SS2 but Gohan's Ki was dropping by the minute, I believe he gained such a boost right when Vegeta distracted Cell, releasing all of his power right then and there.
Perfect Cell: 935,000,000
-- vs Goku: 2,625,000,000
-- vs Gohan: 3,150,000,000
----- full power: 3,300,000,000
----- powered-up: 4,620,000,000
--Super Perfect Cell: 6,600,000,000
Cell powered-up many times throughout the entire fight. Trunks says Cell committed the same mistake as himself when he charged up power and entered his bulky form. So, considering the gap between Grade 2 and 3 is ~1.4x, I thought it's be acceptable to apply it here as well. Cell, when he comes back, says he has powered-up like Gohan, and seems to have acquired his own equivalent of Super Saiyan 2, so it's likely he boosted his power from his Perfect form by 2x. Yes, I think Super Perfect Cell was stronger than Gohan.
Piccolo: 1,350,000,000
Future Trunks: 21,000,000
-- Super Saiyan: 1,050,000,000
-- Grade 2: 1,470,000,000
Vegeta: 21,500,000
-- Super Saiyan: 1,075,000,000
-- Grade 2: 1,505,000,000
Cell Jr: 1,450,000,000
When Piccolo asks Goku if he stands a chance against Cell, Goku says no, and Trunks is surprised, which implies Piccolo is at least stronger than 50% MSS Goku. Vegeta and Trunks trained to get to around that level of power too, so they're stronger than 50% MSS Goku as well.
Future timeline: ---------------------------------
Future Gohan: 2,000,000
-- Super Saiyan: 100,000,000
Future Trunks: 30,000
-- Super Saiyan: 1,500,000
Artificial Human #18: 205,000,000
Artificial Human #17: 210,000,000
#17 said he didn't even use 50% of power against Gohan the last time they fought (presumably, that's what Gohan trained to surpass), so Gohan was really weak, but at least he was stronger than he was once Mecha Freeza arrived. The androids are at a level where Trunks could take them both on alone, like he tells us when he comes to fight the androids in the present timeline.
Future Trunks: 21,000,000
-- Super Saiyan: 1,050,000,000
-- 3 years later: 48,000,000
----- Super Saiyan: 2,400,000,000
Imperfect Cell: 440,000,000
I don't know if Trunks was a MSS by the time he killed the androids. His aura implies so, but he wouldn't have enough time to master it. He's a MSS three years later though, he has to be. Cell was stronger than the androids and most versions of Future Trunks, so I usually just give him the same value as the other Cell once he absorbed humans.