Gasoline will soon cost more than $1 a gallon. Filling stations will have to convert their pumps, which now can post no price higher than 99.9 cents.

We're told that this is a Very Important Problem because the conversion will cost $100 million. However the magnitude of the crisis appears to me to be somewhat less than titanic.

There are now more than 100 million vehicles on the road. When the cost of converting gas pumps is apportioned among all motorists, the one-time charge would be less than $1 per vehicle. Filling stations could recapture their costs by raising gasoline a penny a gallon for about 10 weeks. Big deal.

Two suggestions have been made to save the $100 million. One is to set the pumps for one-tenth of the real unit price, then multiply the final bill by 10.

Example: If gas is $1.08, the price would be posted as 10.8 cents per gallon. Five gallons would register as $0.54. Attendants and customers would multiply 54 cents by 10 and arrive at the correct total, $5.40.

I vote "No" on that one. Many attendants and customers would need pencil and paper to do the arithmetic.

The second suggestion, now being actively pushed by the U.S. Metric Board and others, is to sell gasoline by the liter instead of by the gallon.

A liter is comparable to a quart, not a gallon, and is almost 6 per cent larger than a quart. When gas hits $1 a gallon, a liter would cost about 26.5 cents.

If you're adamantly opposed to using metric measurements, you'll be quick to point out that there's no need to switch to liters. Just sell gas by the quart instead of by the gallon. Instead of $1 a gallon, make it 25 cents a quart.

Your argument would be valid. However, I think we will eventually be won over by the simplicity and logic of the metric system. So why procrastinate? Pulling a tooth slowly doesn't ease the pain. If we're going to switch to metric eventually, the best course may be to bite the bullet (9 mm., of course) and get it over with.

Two obvious difficulties will mark the switch to metric measurements. One is inertia; people don't like to be forced into new patterns of activity. The other is uncertainty; people who don't know how to make quick comparisons between the two systems fear they're being cheated.

Ellen Aaron says some rule-of-thumb comparisons are already coming into vogue. One is, "A liter is one martini more than a quart."

One who is buying 60 liters of gasoline might want to have more precise information about the size of that martini.The best I have been able to work out is that a liter holds 1.0570824 times as much as a quart. A quart's 32 ounces compare to the 33.826636 ounces in a liter. Your martini would therefore consist of less than 1.83 fluid ounces. That's a mighty puny martini.

If advocates of the metric system want to move their cause forward, I think the most effective thing they could do would be to flood the country with free comparison charts - some in large type, to be posted on walls, some in small type, to fit on wallet-sized cards.

When everybody knows how to convert quarts to liters, miles to kilometers and pounds to kilograms, our fear of the unknown will begin to diminish. We will be much more receptive to the logic of switching to a system that uses multiples of 10.

Many years ago, we decided to base our money on the decimal system. Ten pennies make a dime, 10 dimes make a dollar. Would you have preferred 20 shillings to a pound and 12 pence to a shilling?

What's the logic in a mile that's made up of 5,280 feet, an acre that contains 43,650 square feet, or a rod that's 16 1/2 feet long? The metric system does it all with multiples of 10.