A body fat calculator is accurate but if you use different calculators you may see slightly different results.
If your objective is to lose weight, you may be tempted to use a simple bodyweight scale to track your progress, but your body fat percentage will tell you more.
When you are trying to lose weight, improve your health, or increase your fitness level, fat loss should be your aim, not just weight loss. You want to maintain the lean mass (fat-free mass) that your body requires.
Changes in body fat percentage might tell you how successfully your exercise or weight loss programme is assisting you in losing fat while keeping fat-free mass.