See what rounding costs on your bill
Type an amount. You'll see what you pay when it is squeezed onto a whole penny, and what you'd pay on a tenth-of-a-penny grid.
Money that only moves in steps of one penny
The smallest coin is the penny, and every till, card reader and bank transfer settles to whole pence. Prices don't. A supplier works out what you owe to a fraction of a penny, then the total is squeezed onto a whole one.
Somebody has to choose whether to go up or down. That somebody is the seller's system, not you. Each squeeze is small, at most a penny. But it happens on every bill, every basket and every transfer, and you never see it, because the pennies you were charged look like the price.
A penny is 1% of a pound. On a £2 loaf that is 0.5%. On a 40p item it is 2.5%. The cheaper the thing, the more one step weighs.
Ten times the precision. Three small coins.
Keep the pound at 100p. Add a half-penny, a fifth-penny and a tenth-penny. Show prices and settle payments to a tenth of a penny. Every £1 now has 1,000 steps.
| Coin | Worth | Coins to make £1 |
|---|---|---|
| Half-penny | 0.5p | 200 |
| Fifth-penny | 0.2p | 500 |
| Tenth-penny | 0.1p | 1,000 |
The names follow the ones we already use. A coin is named for what fraction of a penny it is worth: a half, a fifth, a tenth.
What changes
- Prices and totals can be shown and settled to 0.1p.
- Three small coins join the ones we already have.
- Software stores money in tenths of a penny.
What stays exactly as it is
- The pound is still 100p.
- It is still base ten.
- The pound and the penny keep their names.
- Nobody has to learn any new arithmetic.
Why we should do it
Ten times finer, from day one
Rounding can add up to 1p to a payment today. On the tenth-penny grid it can add 0.1p at most. When a seller rounds up, the average extra falls from 0.5p to 0.05p. Nothing else you can do to a price system cuts the error by ten in one move.
Nothing new to learn
Same pound, same pence, same base ten. If you can read 139.9p at a petrol pump, you can read a price to a tenth of a penny.
Bills payable exactly
A supplier works out your energy bill to a fraction of a penny. Today the total is rounded onto a whole penny, and when it rounds up you pay up to a penny too much. On the tenth-penny grid it is payable to a tenth. The supplier gives up at most a penny a bill, which was never its margin, so it stays in business. You keep the money, so it gets spent. Wholesale prices, taxes and network costs don't change. The rounding on top of them goes.
Fair splits
Split £10 three ways. Today two people pay £3.33 and one pays £3.34. On the tenth-penny grid it is £3.333, £3.333 and £3.334. The gap between the person who pays most and the person who pays least falls from 1p to 0.1p.
Prices that follow costs both ways
Costs move in small steps. A coarse grid can push sellers to round up to stay safe, so prices rise in jumps. With ten times as many steps, a price can rise and fall with cost in small moves.
The cheapest reform on the table
No new currency. No relearning. For software it is a change of unit on one agreed date. For cash it is three coins, and digital payments need not wait for them.
It repeats on every payment
Ten payments a week, each rounded up by half a penny on average, come to about £2.60 a year today and about 26p on this proposal. That is for one person, on one habit, and it repeats every week, for ever, across every payment we make.
How it works, in plain terms
The price
Every price and total is kept to a tenth of a penny. £61.372 means 61 pounds and 37.2 pence. Fuel prices already work like this.
The rule
Round once, at the final total, to the nearest tenth of a penny, with halves going up. Never round line by line, and never round in the seller's favour. Rounding to the nearest averages out to zero, so it favours nobody.
In software
Store money as whole tenth-pennies, so £1 is 1,000 units. Changing the unit of storage is the work. The arithmetic doesn't change, so any till or bank system that already handles money as a whole number of pence can be adapted to it.
The switch
- Fix one format and one date, published well ahead, so every system builds to the same rule.
- Run an overlap in which systems accept and show both whole-penny and tenth-penny amounts.
- On the date, digital settlement moves to tenths of a penny.
- Strike the three coins and release them.
- Until the coins are in circulation, cash rounds to the nearest half-penny.
Cash
Cash is where the size of the coin bites. A tenth-penny coin may cost more to make than it is worth. That is why the plan doesn't depend on it. Digital payments can carry most of the gain, and cash rounds to the nearest half-penny until the coins arrive.
Try it: splitting a bill
Share a bill between friends. See how far apart the shares end up today, and on a tenth-penny grid.
Straight answers to the obvious questions
Is it too small to matter?
On a single payment, yes, at most a penny. The case is that it costs very little, works on every payment we make, and cuts the error by ten. We don't claim it fixes the cost of living. We claim it removes an avoidable surcharge from every bill.
Will this lower my energy and fuel bills?
It removes the rounding added on top of them, at most a penny a bill today. It doesn't change wholesale prices, taxes or network charges, which set most of the bill.
Won't the tiny coins cost more than they're worth?
The tenth-penny and fifth-penny might, which is why the plan doesn't lean on them. Digital payments settle to a tenth of a penny without any coin, and cash rounds to the nearest half-penny until coins are worth making.
Can shops just keep rounding up?
The rule is to round once, at the total, to the nearest tenth of a penny. Even a seller who ignored it could add at most 0.1p to a payment, instead of the 1p they can add today.
Can the systems really cope?
Storing money in tenths of a penny is a change of unit, not a new kind of arithmetic. The real work is agreeing one format and one date so every system moves together, which is why the plan includes an overlap period.
Don't petrol pumps already do this?
Yes, prices such as 139.9p a litre are normal. That shows people already read tenths of a penny without trouble. The change is to let the final total settle to the same precision.
What we're asking for
- Settle every digital payment to a tenth of a penny.
- Introduce the half-penny, the fifth-penny and the tenth-penny.
- Round once, at the total, to the nearest step.