You’ve done your homework on understanding how debt works and decided to take on a loan. No matter whether that loan is a mortgage, personal loan or credit card then the next step is to ensure that you end up with the cheapest or lowest cost loan you can, along with one that actually meets your needs. To do this you have no choice but to find a quiet place, where with a fresh cup of tea, you can read the small print of each loan provider you are considering and in parallel run some maths to calculate who is the cheapest provider based on all that small print. It’s key to do the maths because when it comes to loans, as with investments, small amounts over long periods and fees matter.
If you want to do the maths yourself then Excel’s PMT function will get you a long way. This gives the repayment amount for a loan given an interest rate, the number of constant periods the loan is taken over and the present value of the loan. If you don’t have Excel or aren't mathematically savvy then you could also use a loan or mortgage calculator to do a lot of the work for you.
Let’s look at a few simple case studies, which build in complexity, to show just how important it is to run the numbers.
At first glance it doesn’t seem like much of a difference. After all it’s only £2.46 per month however this is no different to the Latte a Day case study I’ve run before which demonstrates how small amounts matter. Over the 10 year period the total interest paid is £2,728 and £3,023 respectively. That 0.5% actually means 10.8% more in interest payments. It’s also important to remember that the longer the loan period the worse this effect. For example lengthen the loan term to 20 years and that 10.8% becomes 11.5%. This is Compound Interest at work.
If you want to do the maths yourself then Excel’s PMT function will get you a long way. This gives the repayment amount for a loan given an interest rate, the number of constant periods the loan is taken over and the present value of the loan. If you don’t have Excel or aren't mathematically savvy then you could also use a loan or mortgage calculator to do a lot of the work for you.
Let’s look at a few simple case studies, which build in complexity, to show just how important it is to run the numbers.
Case Study 1 - All else being equal secure the lowest interest rate you can
Bank A is offering a loan with an annual interest rate of 5% (the interest rate) and Bank B has a rate of 5.5%. The loan amount is for £10,000 (the present value of the loan), you are going to make the repayments monthly and you intend to take the loan over 10 years (the number of constant periods will be 10x12=120 months because you pay monthly). To calculate the monthly repayment for the first scenario you would enter the following into Excel ‘=PMT(5%/12, 10*12,-£10,000)’ which would give you a repayment to Bank A of£106.07 per month. Note you have to divide the interest rate by 12 months as the repayment is made monthly. If you run the same calculation for Bank B’s interest rate of 5.5% the monthly repayment would be £108.53.At first glance it doesn’t seem like much of a difference. After all it’s only £2.46 per month however this is no different to the Latte a Day case study I’ve run before which demonstrates how small amounts matter. Over the 10 year period the total interest paid is £2,728 and £3,023 respectively. That 0.5% actually means 10.8% more in interest payments. It’s also important to remember that the longer the loan period the worse this effect. For example lengthen the loan term to 20 years and that 10.8% becomes 11.5%. This is Compound Interest at work.