What it means
Most variable rate loans are quoted as a reference rate plus a spread, for example a benchmark rate plus 2.5%, with the spread reflecting the lender's view of your credit risk. The spread normally stays fixed for the term while the reference rate resets on a set schedule, often monthly or quarterly.
For a business this is a genuine risk item rather than a technicality, because a two point rise on a large facility can absorb an entire year's profit improvement. It is also an opportunity, since variable rates typically start lower than fixed rates and fall immediately when central bank rates fall.
Working out the exposure is straightforward: multiply the outstanding balance by the change in rate to see the annual cash effect. A useful discipline is to model the interest bill at the current rate and at two or three percentage points higher, then check whether covenants and cash flow still work.
Many facilities include a cap, a floor or a collar, which limit how far the rate can move in one or both directions. Borrowers can also buy an interest rate swap, which converts a variable rate into a fixed one for a fee, without renegotiating the underlying loan.
The nuance most people miss is that the reset schedule matters as much as the rate itself. A loan that reprices annually gives you a year to react, while one that reprices monthly passes every movement straight through to cash.
In practice
Real-world examples
Example 1
A property developer funds a project on a variable rate facility because it expects to repay within 18 months. Rates rise twice during the build, adding $84,000 to costs, which the contingency budget absorbs.
Example 2
A retailer with a variable rate overdraft models a three point rate rise before signing a new lease. The model shows interest cover falling below the bank's covenant, so it fixes the rate on half the borrowing first.
Example 3
A manufacturer holding surplus cash on a variable rate deposit benefits when the central bank raises rates. Interest income rises by $47,000 over the year with no action from the finance team.
Think of it
A variable interest rate is like riding in a sailboat. When the wind is favorable, you move quickly and save energy. But when a sudden storm hits, you must work harder to stay on course, as the unpredictable gusts push and pull your vessel in different directions.
Formula
Calculation
Interest rate = Reference rate + Margin, and Annual interest = Outstanding balance x Interest rate.
A company holds a $400,000 term loan priced at the benchmark rate plus a margin of 2.5%. With the benchmark at 3.0%, the rate is 3.0% + 2.5% = 5.5%, so annual interest is $400,000 x 0.055 = $22,000, or $22,000 / 12 = $1,833.33 a month. If the benchmark rises to 4.5%, the rate becomes 7.0% and annual interest becomes $400,000 x 0.07 = $28,000, or $2,333.33 a month. The increase is $28,000 - $22,000 = $6,000 a year, which is exactly $500 more each month from the same unchanged loan balance.Case study
Seen in the real world
Peltham Logistics is an invented haulage business used here as an illustrative example. It financed a fleet expansion with $3,000,000 of variable rate debt at a benchmark plus 2.0%, giving an opening rate of 4.0% and interest of $120,000 a year.
Over the following 18 months the benchmark in this fictional scenario rose from 2.0% to 5.0%, taking the loan rate to 7.0% and the annual interest bill to $210,000. Because the loan repriced quarterly, the increase reached the cash flow almost immediately, and the extra $90,000 a year wiped out the efficiency savings the new vehicles had delivered.
The illustrative company's response was to fix two thirds of the balance through a swap and to add a simple rate sensitivity table to every board pack. The remaining variable portion kept some benefit available if rates fell, while the fixed portion made the budget behave predictably again.
Watch out
Common mistakes
- Comparing a variable rate today with a fixed rate today and choosing the lower number, without asking what happens if rates move by two or three points.
- Forgetting that the margin above the benchmark can be reset by the lender at review, so even the fixed part of the pricing is not permanent.
- Budgeting a full year of interest at the opening rate, which understates cost as soon as the first reset arrives.
Questions
People also ask
What is a reference or benchmark rate?
It is a published market rate that lenders use as a common starting point, and your loan rate is that benchmark plus an agreed margin.
Is a variable rate always cheaper than a fixed rate?
Not always, it usually starts lower because the borrower is carrying the risk of future rises, but over a full cycle it can end up costing more.
What is an interest rate cap?
It is an agreement, bought for a fee, that limits how high your variable rate can go, so you keep the benefit of falls while putting a ceiling on rises.