Hope this is clear
A "quick" way to work out debt consolidation is weighted average method.
You look at all your debt and what it will, in reality, cost to repay it.
100 at 10%
300 at 12%
600 at 4%
1000 at ??
Borrowed+repay cost
Borrowed
(100+10)+(300+36)+(600+24)
100+300+600
1000+70
1000
So you repay @ 7%
This⬆️ calc is simple interest and paid on time. Normally you repay some of the debt with each repayment and are charged interest.
So you will be paying compound interest (APR) on your borrowings so most debt will be at different rates and different time lengths and/or you need to adjust because you can't repay the full amount of each debt each pay period.
You can use an online calculator (eg a mortage calculator) to work out what you think you will pay for each debt
You can also add in other charges if you are paying a company to manage your debt.
Eg £20 flat fee
1000+70+20
1000
So you repay @ 9%
You can calculate if the consolidation loan plus interest and other charges are less than or more than your current debt and total expected interest.
Sometimes paying more over a longer period is the best option as you can keep to a managed budget and don't run the risk of missing a payment on a high interest loan.
Eg a missed payment is new "mini" loan or an extra cost of borrowing and you need to repay the loan and a new loan with interest on both
100 at 10% => 110@10%
300 at 12% => 336@12%
600 at 4% => 624@4%
( 100 110+ 10 11 )+(300+36)+(600+24)
100+300+600
1000+36+74.32
1000
So you repay @ 11.032
%
(100+10)+( 300 336 + 36 40.36)+(600+24)
100+300+600
1000+36+74.32
1000
That's where budgeting advice can be very helpful as it set out your day to day costs, the occasional costs and adds a little for the unexpected