What the tools are actually for

How a 28-year-old first-time buyer used the mortgage tool twelve times in a week

From "I don\'t know what I can afford" to a completed offer in 14 days

The problem

"I was looking at two-bed flats in south Manchester, prices were £180k to £240k. I had £22,000 saved and no idea what I could actually borrow. Every bank\'s calculator gave me a different number, and none of them explained why. I went to an appointment with a mortgage broker who said I\'d probably get offered around £180k but wouldn\'t commit. I came home and opened a browser tab."

The approach

He spent an evening on the site, then three more evenings over the next week. The order was:

• Affordability calculator to figure out the realistic monthly payment he could carry (not the maximum the lender offered — they were different by about £300/month).
• Stamp duty calculator to add the £100–£1,500 of stamp duty he\'d have to pay at that price range. Most buyer-facing estimates he\'d seen were wrong by hundreds of pounds.
• Mortgage repayment calculator with the actual rate from a MoneySupermarket comparison, not the headline rate. The difference was £41/month on his numbers.
• Total interest paid view, with a sober moment about the total cost over 25 years.
• Overpayment calculator to see what £200/month extra would do to the term and the total interest. It cut 4 years and 11 months off the term, saving £26,400 in interest.
• Lease vs buy calculator to sanity-check the rent-vs-buy assumption, because the area had a lot of rental stock at comparable price.

The result

"I went back to the broker with a single sheet of A4 and six specific numbers. He said it was the first time a first-time buyer had walked in with that kind of prep. I had a mortgage offer accepted at £195,000, with a 4.79% 2-year fix and a 25-year term, and an overpayment plan that would bring the term down to under 20 years. Without the site I would have either offered too much and been rejected, or offered too little and been outbid."

Twelve separate sessions across one week. Total time: about 3 hours. The mortgage offer was completed three weeks later.

How a Year-9 maths teacher used the site to teach compound interest for the first time

From "the textbook version is too abstract" to "every student got the concept in 25 minutes"

The problem

"The textbook version of compound interest is the one with the £1,000 invested at 5% a year for 20 years. Half the class doesn\'t connect the formula to a number they care about. The other half gets the formula and not the intuition. I needed a way to make the curve visible and let the kids play with it."

The approach

Three lessons, each built around one or two of the site\'s tools, each with a worksheet she wrote around the tools:

Lesson 1 (50 min): The shape of the line. Open the compound interest calculator with three side-by-side scenarios — £100 saved, £100 invested, £100 borrowed at the same rate — and let the students see the curves diverge. "Most of the class noticed the gap widening, which is the point."

Lesson 2 (50 min): The rule of 72. Pair the compound interest calculator with the rule-of-72 estimator. Get each student to pick a rate and a starting amount and predict when their money would double, then check.

Lesson 3 (50 min): Why it matters for your savings and your debt. Use the same calculator with credit-card rates, then with student-loan rates. The point: the same math produces very different feelings.

She also used the BMI calculator briefly to show how a "single formula, simple inputs" tool can be misleading without the right caveats — the discussion of "is this tool good or bad" became a whole separate lesson.

The result

"I had 28 students in the class. On the end-of-topic assessment, 24 of them could explain in writing why the savings line is a curve and not a straight line, and why early saving is more powerful than late saving. That is the highest score I have had on this topic in seven years of teaching it. The tool did the lifting. I just framed the question."

How a sole trader cut invoicing time from 2 hours a week to 20 minutes

From a Word template and a calculator to a one-screen workflow

The problem

"I do small carpentry jobs for builders and householders. I was invoicing on a Word template, with a calculator open in another tab. Each invoice was about 8 minutes. End of the month was about 2 hours. I also had a few invoices that went out with the wrong VAT, which is expensive to fix and embarrassing to explain."

The approach

The fix was a one-time setup followed by a new habit:

• Invoice generator as the new template. Each invoice auto-calculates subtotal, VAT (20%), and total. No more mental arithmetic, no more wrong-VAT mistakes.
• Time tracking for jobs billed by the hour. He built a small mental rule: every job is started and stopped in the tool, and the end-of-week invoice pulls straight from the log.
• Unit price calculator for the materials-heavy jobs (decking, fencing). He uses it to sanity-check supplier quotes against his own cost.
• Tax estimate to set aside the right amount each month so the January self-assessment isn\'t a surprise.

The result

"End-of-month invoicing is now about 20 minutes. I send invoices the same day I finish the job, which means I get paid faster — average debtor days dropped from 21 to 11. I have not had a wrong-VAT invoice since I switched. The site has paid for itself many times over, and I have not had to give anyone my email address to use it."