As an academic at Oxford university I don’t have an enormous salary, but even so I have made a pledge to donate £1m to charity over the course of my working life.

It wasn’t an easy decision, but I chose to do this after realising just how much more good my money could do for others than for me. I’m a research fellow in ethics, and my thoughts on the ethical issues around global poverty have had a dramatic impact on my personal behaviour.

Philosopher Peter Singer—a fellow Australian—said that the money we spend on luxuries could be used to save people’s lives in developing countries if we so wished. How then can we justify choosing the luxuries? This is a strong argument, and quite confronting. So I asked myself what standard of living is justifiable. How little could I live on? The figure I came to is around £10,000 a year, including rent, clothes, food, and holidays.

I’m happy to continue the relatively frugal lifestyle I had as a graduate student—it’s certainly much better than what most people in the world can afford. I have a nice place to live, a good computer and phone. The things that are most important to me cost very little: such as spending time with my wife and friends, reading books, and listening to music.

I am 31, so I can expect to work for another 35 years. My annual salary over that time will average about £45,000. After tax this should allow me to give away an average of £30,000 a year—amounting to slightly more than £1m by the time I retire. Last year I earned £25,000 before tax and gave away £10,000 of it. I also managed to save some money toward buying a house with my wife, which we will live in, then eventually sell and give away the proceeds.

I do my giving at the end of each year. I’ve researched which charities are the most effective, and this has led me to support those fighting tuberculosis and parasitic infections in the developing world.

Between 1994 and September 2010, the Bill & Melinda Gates Foundation made grants worth $23.9 billion. Two anonymous donors last year gave £250,000 so that Gipsy Moth IV, the yacht in which Francis Chichester single-handedly circumnavigated the globe in 1967, could remain in Britain. An anonymous benefactor stepped in after a couple in Louisiana lost their home in 2007 in the wake of a dispute surrounding a $1.63 property-tax bill and gave them the deeds to the house.

I calculate that the money I give away can save between 2,000 and 10,000 lives (taking into account the total cost of medication, delivery, and administration). Compared with this, the benefit that I would get from spending the money on myself is clearly quite insignificant. Indeed, there are strong arguments that by donating to the most cost-effective charities, your money goes more than 10,000 times as far as if you spend it on yourself.

I’m not doing this alone. I’ve started an organization called Giving What We Can, which has 64 members (including Peter Singer). Each of us has pledged to donate at least 10 percent of our earnings to wherever we think it can do the most good. My wife, Bernadette, an NHS doctor, has supported this from the beginning and will give away everything she earns over £25,000.

As a couple, we don’t think that what we’re doing is really all that sacrificial. We are still left with a joint income that is exceptionally high by world standards. We are donating about a third but are not having to give up the things that really matter to us. In fact, it is probably improving my quality of life. It’s not that it gives me a warm glow, but it does give me a certain peace with myself and a sense of purpose.

Some people suggest I should first make huge amounts of money. My answer is that by doing it my way I have attracted others to join me—and our collective giving will be far more substantial than anything I could have made on my own. Together, the members of Giving What We Can have pledged to donate £14m over the course of our careers, which should save between 30,000 and 100,000 lives. I’m not sure I could have made that much for charity by playing the markets.