Sod’s Law: A Proof

By Dr. David Lewis, Dr. Keylan Leyser and Philip Obadya
Commissioned by British Gas, Leeds, UK.

When British Gas commissioned scientists to create a formula to predict Sod's Law we wanted part of the action. We didn't get it, but we did manage to get hold of the plucky scientists' report. Here it is:


We have finally proven a rule mathematically that which we all know is perfectly obvious each time our email crashes as an important deadline looms or the shower runs icily cold seconds after we’ve lathered ourselves up. In this report e supply the statistical formula for predicting occurrences of Sod’s Law

Furthermore we find, based on over 1,000 people’s experiences, that the original Sod’s Law - ‘anything that can go wrong, will go wrong’ - is only half the story. It can now be improved by the use of a new rule - ‘Things don’t just go wrong, they do so at the most annoying moment’.

This explains why your email will most likely crash as you try to send something important, how the chances of your spilling a drink down your clothes are highest just before a date, and why it’s a safe bet that your heating will most often break down during a cold snap.

Previous studies have shown that Sod’s Law isn’t a myth - toast will fall butter-side down, odd socks do breed and string can tie itself in knots. Our formula now allows people to calculate the chances of Sod’s Law striking, and thus try to beat it.

Five factors are taken into account with any task to allow us to calculate its R_SL-value, the Sod’s Law rating. Urgency (U), complexity (C), importance (I), skill (S) and frequency (F) are scored between 0 and 9.

We set a further factor, aggravation (A), at a constant value of 0.7 following a poll of over a thousand people. Sod’s Law ratings (R_SL) can range from between 0 and 8.6, with higher numbers making it more likely that bad luck is right around the corner.

The mercilessness of Sod’s Law becomes apparent from our research. Not only do things go wrong, they do so when they are most likely to drive us up the wall. For example, Sod’s Law shows quite how cruel it can be when we investigate the case of the cold shower a little more closely. A poll of participants showed that the importance factor (I) of having nice warm water when washing hair is much higher, on average, for women (I = 7) than it is for men (I = 2). It follows from the formula that, due to this difference, Sod’s Law is more than 50% more likely to strike and turn the water cold when a lady is showering than when a man is in the shower (Figure 1). This is in agreement with rigorous anecdotal evidence.

The lesson from this is that, to cut the seemingly unbeatable Sod’s Law Gremlins down to size you need to change one of the elements in the equation. So, if you haven’t got the skill to do something important, leave it alone. If something is urgent or complex, find a simple way to do it. If something going wrong will particularly aggravate you, make certain you know how to do it. For example, you spill a drink on yourself before a date because, making the urgent and important decision of what to wear, you forget all you ever knew about getting a cup to your lips and throw tea down yourself. So concentrate harder on drinking.

When emailing an important document anxiety will make it more likely that you will hit one of those mysterious keyboard combinations that make everything vanish. Try not to let your computer know that you’re in a hurry. Table 1 shows likelihood and annoyance scores for a range of common Sod’s Law events, which should be used as a daily reference.






There is, of course, a Sod’s Law element to using the equation as well. So beware. If you judge your ratings wrongly you might become too optimistic, allowing calamity to strike. Furthermore, knowing a priori the R_SL value of a particular task may well lead to over-confidence, producing a positive feedback mechanism by which the Sod’s Law rating increases still further.

We now provide seven steps to forecasting a potential Sod’s Law moment, so you can work out which factors you need to change to try and avoid it.

How to calculate the Sod's Law Rating of a task:

1. Rate the urgency, importance and complexity of the task on a scale of 1 to 9 and add these figures together.
2. Rate how skilled you are at the task. Subtract this from 10.
3. Multiply your answers to steps 1 and 2 together and divide by 20.
4. Rate from 1 to 9 how frequently you perform the task and divide this by 10.
5. Calculate the sine value of your answer to step 4 (you’ll find this a ‘sin’ on most calculators) and subtract this from 1.
6. Divide 1 by your answer to step 5.
7. Finally, multiply your answer to step 3 by 0.7, and then multiply this by your answer to step 6. Voila - you have your Sod’s Law rating.
8. The closer to 10 it is, the higher your risk of falling victim to Sod’s Law.

Of course, by the time you’ve twice got as far as step 5 to then forget a vital number, started again only to get up to the beginning of step 7 when the batteries in your calculator run out the urgency rating of your original task has probably gone up much more!


British Gas commissioned Dr. David Lewis, a chartered psychologist; Dr. Keylan Leyser, an economist and business consultant; and Philip Obadya, a mathematician, to devise the formula. Likelihood scores are for a typical adult and are based on the Nationwide survey of 1023 adults, conducted by Taylor Nelson Sofres (TNS) that the team used to test their work.

Original here