1500 W → 1300 W — time ×1.154

Same oven

Look at the plate inside the door or on the back. Careful, though: two numbers may be printed there. Input power and cooking output are different, and the one to use is the **cooking output**. A unit drawing 1400 W often cooks at 900 W — the input figure is usually the larger one.

It is an inverse proportion

New time = old time × (old wattage ÷ new wattage). Three minutes at 700 W becomes 3 × 700 ÷ 1000 = 2:06 at 1000 W. More power means less time, and when the two wattages match the multiplier is one and nothing changes.

The energy matches, the evenness may not

This conversion only matches the energy delivered. Higher power packs that energy into a shorter burst, so the outside heats first while the middle lags. Splitting the converted time in half and stirring between the two runs works better — especially for liquids and thick pieces.

Nearby wattages

Same packet wattage

Not the same as turning the power level down

A household microwave cannot really dial its power down; it switches full power on and off to average it out. So “50 % for four minutes” and “100 % for two” deliver the same energy but not the same result — the first leaves time between bursts for heat to spread inward. This table converts between ovens, not between power levels.

How to read this

• New time = old time × (old wattage ÷ new wattage).
• When the two wattages match, the multiplier is one and the time stands.
• Use the cooking output on the plate, not the input power.
• Check at about eighty per cent of the calculated time and add short bursts.