Remortgage Savings Calculator

Dropping from 6% to 4.5% on a 200,000 mortgage saves about 180/month. Over a 2-year fix that's 4,320 before switching costs. Typical switching costs 1,500 (ERC if applicable plus new arrangement fee) leaves 2,820 net savings. potentially useful. Higher fees or shorter fix periods can flip the answer.

A worked example

Try the defaults: current monthly payment of 1,289, new monthly payment of 1,109, switching costs of 1,500, new fix period of 24. The tool returns 2,820.00. You can adjust any input and the result updates as you type — no submit button, no reload. That's the real power here: seeing how sensitive the output is to one or two assumptions.

What moves the number most

The result responds to Current Monthly Payment, New Monthly Payment, Switching Costs, and New Fix Period. Not every input has equal weight. Adjusting one input at a time toward extreme values shows which ones move the result most.

The formula behind this

Monthly gap × months minus switching costs. Everything the calculator does is shown in the formula box below, so you can check the math against your own spreadsheet if you want.

Stress-testing the plan

Run the calculation at your current rate, then run it again at a rate 2–3 percentage points higher. That's roughly what a product reset could bring at renewal, and it's a useful check on whether you can afford the mortgage in a higher-rate world, not just today's.

What this doesn't capture

The figure excludes arrangement fees, valuation costs, legal fees, insurance, and any early-repayment charges — those can add several thousand to the headline cost. Rate changes at renewal for fixed-term deals will shift the picture further. Use this for the core interest/principal math and add the other costs on top.

Common scenarios

Remortgage savings calculations matter in several contexts:

• When interest rates fall and your current fixed rate ends, comparing the new product against staying on the reversion rate
• During a wider rate-cycle change, to model how long it takes switching costs to pay for themselves
• When assessing whether to exit an early-repayment charge and move to a better deal
• Comparing multiple product offers from different lenders to rank them by net financial outcome

What the result shows and does not show

The calculator models the net cash difference between your current monthly outgoings and new ones, minus a one-time switching cost, over your chosen fix period. It answers: "How much money do I keep, after paying to switch, over the life of this new deal?"

It does not capture:

• Changes to the mortgage balance (capital repayment) — only the payment difference matters here
• Timing of costs (switching expenses paid upfront, savings spread across months)
• Rates beyond the new fix period
• Redemption penalties, valuation fees, or legal costs not entered as switching costs
• Any overpayments or lump-sum payments you might make

Educational illustration

This tool is for numerical illustration and learning. The output models one specific scenario based on the figures you enter. Real-world outcomes depend on rates, product availability, personal circumstances, and costs that vary by lender and jurisdiction. Use the result as a starting point for comparison, not as a forecast or guarantee of savings.