Figure Simple Interest Calculator

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figure simple interest calculator
Interest (I)Principal (P)Rate (R)Time (T)
YearsMonthsDays
Answer:
Enter values and click Calculate.
function toggleInputs(){var mode=document.getElementById('solve_for').value;document.getElementById('row_p').style.display=(mode==='P')?'none':'table-row';document.getElementById('row_r').style.display=(mode==='R')?'none':'table-row';document.getElementById('row_t').style.display=(mode==='T')?'none':'table-row';document.getElementById('row_i').style.display=(mode==='I')?'none':'table-row';}function calculateResult(){var mode=document.getElementById('solve_for').value;var p=parseFloat(document.getElementById('p_val').value);var r=parseFloat(document.getElementById('r_val').value);var t=parseFloat(document.getElementById('t_val').value);var i=parseFloat(document.getElementById('i_val').value);var unit=document.getElementById('t_unit').value;var showSteps=document.getElementById('steps').checked;var ansBox=document.getElementById('answer');var resText="";var t_years=t;if(unit==='months'){t_years=t/12;}else if(unit==='days'){t_years=t/365;}if(mode==='I'){if(isNaN(p)||isNaN(r)||isNaN(t)){alert('Please enter P, R, and T');return;}var interest=p*(r/100)*t_years;var total=p+interest;resText="Interest (I) = $"+interest.toLocaleString(undefined,{minimumFractionDigits:2,maximumFractionDigits:2})+"
Total Principal + Interest = $"+total.toLocaleString(undefined,{minimumFractionDigits:2,maximumFractionDigits:2});if(showSteps){resText+="
Steps:
1. Formula: I = P × r × t
2. Convert Rate: "+r+"% = "+(r/100)+"
3. I = "+p+" × "+(r/100).toFixed(4)+" × "+t_years.toFixed(4)+"
4. I = "+interest.toFixed(2)+"
";}}else if(mode==='P'){if(isNaN(i)||isNaN(r)||isNaN(t)){alert('Please enter I, R, and T');return;}var principal=i/((r/100)*t_years);resText="Principal (P) = $"+principal.toLocaleString(undefined,{minimumFractionDigits:2,maximumFractionDigits:2})+"";if(showSteps){resText+="
Steps:
1. Formula: P = I / (r × t)
2. P = "+i+" / ("+(r/100).toFixed(4)+" × "+t_years.toFixed(4)+")
3. P = "+principal.toFixed(2)+"
";}}else if(mode==='R'){if(isNaN(i)||isNaN(p)||isNaN(t)){alert('Please enter I, P, and T');return;}var rate=(i/(p*t_years))*100;resText="Rate (R) = "+rate.toFixed(3)+"% per year";if(showSteps){resText+="
Steps:
1. Formula: R = (I / (P × t)) × 100
2. R = ("+i+" / ("+p+" × "+t_years.toFixed(4)+")) × 100
3. R = "+rate.toFixed(3)+"%
";}}else if(mode==='T'){if(isNaN(i)||isNaN(p)||isNaN(r)){alert('Please enter I, P, and R');return;}var time=i/(p*(r/100));resText="Time (T) = "+time.toFixed(3)+" Years";if(showSteps){resText+="
Steps:
1. Formula: t = I / (P × r)
2. t = "+i+" / ("+p+" × "+(r/100).toFixed(4)+")
3. t = "+time.toFixed(3)+" years
";}}ansBox.innerHTML=resText;}

Calculator Use

The figure simple interest calculator is a specialized financial tool designed to compute any of the four variables in the simple interest formula: Interest, Principal, Annual Interest Rate, or Time. Simple interest is most commonly used for short-term loans, certain types of consumer credit, and basic savings vehicles where interest is only calculated on the initial amount deposited or borrowed.

By using this calculator, you can quickly determine how much a loan will cost you over time or how much your savings will grow. Unlike compound interest, simple interest does not "interest on interest," making it much easier to figure out manually or with our dedicated tool.

Principal (P)
The original sum of money borrowed or invested.
Rate (R)
The percentage of the principal charged as interest per year.
Time (T)
The duration for which the money is borrowed or invested, usually expressed in years.
Interest (I)
The actual dollar amount earned or paid over the specified time period.

How It Works

When you need to figure simple interest, the math revolves around one fundamental algebraic equation. The formula used by this calculator is:

I = P × r × t

Where:

  • I is the Interest Amount.
  • P is the Principal Amount.
  • r is the Annual Interest Rate (decimal form).
  • t is the Time in years.

If you are solving for other variables, the formula is rearranged:

  • To find Principal: P = I / (r × t)
  • To find Rate: r = I / (P × t)
  • To find Time: t = I / (P × r)

Calculation Example

Scenario: You borrow $5,000 from a friend at a simple interest rate of 4% per year. You plan to pay them back in full after 3 years. How much interest will you owe?

Step-by-step solution:

  1. Identify Principal (P) = $5,000
  2. Identify Rate (R) = 4% (which is 0.04 as a decimal)
  3. Identify Time (T) = 3 years
  4. Calculate: I = 5,000 × 0.04 × 3
  5. I = 200 × 3
  6. Interest (I) = $600.00
  7. The total amount to be repaid would be $5,600.00.

Common Questions

What is the difference between simple and compound interest?

Simple interest is calculated only on the principal amount of a loan or deposit. Compound interest is calculated on the principal amount and also on the accumulated interest of previous periods. Compound interest grows faster over time, whereas simple interest remains constant per period.

How do I calculate simple interest if the time is in months?

The formula requires time (t) to be in years. If your timeframe is in months, divide the number of months by 12. For example, 6 months is 0.5 years. Our figure simple interest calculator handles this conversion automatically when you select "Months" from the dropdown menu.

Is simple interest used for mortgages?

Generally, no. Most modern mortgages use a form of compound interest where interest is calculated monthly based on the remaining balance. However, some "Simple Interest Mortgages" do exist where interest is calculated daily on the outstanding principal balance. It is important to check your specific loan agreement.

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