4 sentences

1. 他竟然在背后算计自己的好朋友。

   tā jìng​rán zài bèi​hòu suàn​ji zì​jǐ de hǎo péng​you.

   He actually plotted against his own good friend behind their back.

   Source: Dong Chinese Dictionary

2. 那个人阴险狠毒，总是背地里算计别人。

   nà gè rén yīn​xiǎn hěn​dú, zǒng​shì bèi​dì​li suàn​ji bié​ren.

   That person is insidious and ruthless, always plotting against others behind their backs.

   Source: Dong Chinese Dictionary

3. 我算计着他明天下午就能到家。

   wǒ suàn​ji zhe tā míng​tiān xià​wǔ jiù néng dào​jiā.

   I estimate that he will arrive home tomorrow afternoon.

   Source: Dong Chinese Dictionary

4. 他正在心里算计这块布料能做几件衣服。

   tā zhèng​zài xīn​li suàn​ji zhè kuài bù​liào néng zuò jǐ jiàn yī​fu.

   He is mentally calculating how many pieces of clothing can be made from this fabric.

   Source: Dong Chinese Dictionary