Rent review: interest on back rent (shortfall)
11 May 2025(2025 May) – Calculating interest on back rent following a rent review, many years ago, the author of a letter published in the Estates Gazette wrote about the difference in results that different makes and models of calculators produce. I think it’s something to do with the (behind-the-scenes) number of decimal points and the rounding.
In providing a client with the computations for interest, I use Excel for Mac. I checked using an iPhone 15 Pro Max built-in calculator. The difference was £9.91 less on the iPhone.
When measuring areas, I work to 3 decimal places for the individual calculations and round up to 2 decimal places for the total. Interestingly, when converting imperial to metric and vice versa, other surveyors generally use 6.1 metres for 20 feet even though strictly it’s 6.096 m.
The snag with rounding as you go is that the total is incorrect.
I have designed my database to automatically convert sqm to sqft and vice versa. I have fields for converting metric dimensions to imperial, including duo decimals. To do duo decimals, Bob Bowden taught me how when he was at Montagu Evans.
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