AccountantsWorld has a free estate tax estimator, allowing data entry by groups of assets.

Advisortek has financial-planning calculators for rates of return, portfolio evaluation, retirement and investment diversification.

Assetstream provides an advanced calculator that computes the tax advantages of donating appreciated stock to charity, taking into account both federal and state income tax rates.

Bankrate.com furnishes a variety of online calculators, including: mortgages; small business (profit margins and internal ratios); credit cards; and CDs (laddering, interest, investments and savings goals.)

The Bureau of Public Debt has the Online Savings Bond Calculator for computing the value of EE, E, I bonds and Savings Notes. Its Savings Bond Wizard™ software helps you to inventory and value U.S. savings bonds. Savings Bond Pro(R) is its new savings bond pricing system for finding the valuation of savings bonds by financial institutions, and value tables.

Calculator.com includes a sophisticated currency conversion calculator, a scientific calculator and various calculators for special industries and special purposes, including financial calculators and even an English/Metric unit converter.

Choose to Save has many calculators for consumer use addressing savings-related issues, including college funding, automotive financing, budgeting for expenses and saving, credit card rate and rebate evaluation, and home mortgage analysis.

The Corporate Tax Calculator, from Denver Tax Software, Inc., computes either regular corporate tax, or uses personal service corporation (PSC) rates; handles capital loss carry forwards to the current year; and computes what any capital loss carry forward would be to future years. It treats Internal Revenue Code Section 1231 gains as capital gains and Section 1231 losses as ordinary losses; allows net operating loss (NOL) carry forwards; and, if needed, computes the charitable deduction limitation.

DinkyTown supplies a Roth IRA comparison with a traditional IRA calculator, graphics are included.

Fidelity Investments has an online basic estate calculator for single and married persons that does both current calculations and growth projections. It allows entry of asset and deduction classes and identification of assets by owner.

The Financial Industry Regulatory Authority offers a variety of financial, college, retirement and investment calculators for investors.

Fiscal Agents Financial Tools offers a variety of retirement, mortgage and loan calculators as well as personal planners; all apply Canadian methodology, but many of the calculators are useful to U.S. planners.

Horizon Financial Planning Corporation offers an online 401k retirement planner.

Mortgage-Calc.com includes various online calculators to compute mortgage, mortgage refinancing and consolidation, financial and basic amortization.

Motley Fool Calculators does online comparisons of conventional and Roth IRAs, with explanations and graphs for calculating the results of converting a conventional IRA to a Roth IRA; it includes every imaginable personal financial calculation, including amortizations and retirement projections.

PhilantroCalc for the Web is free via Ashland University as well as other charitable organizations' websites. It includes calculators for charitable gift annuities, CLTs, CRATs and CRUTs.

72t on the Net offers a life expectancy calculator for all commonly used mortality tables, an elaborate compound interest calculator and calculators for both Roth eligibility and Roth conversion.

The Social Security Administration provides online calculators for both basic and detailed calculations of Social Security benefits available to an individual; a more detailed calculator can be downloaded for free.

Stan DiLiberto, CPA, CPF has a variety of retirement calculators, including those that help plan for retirement, pensions, Social Security benefits, retirement income, Roth IRA calculator, traditional IRA calculator and Roth IRA conversion

T. Rowe Price has a number of retirement-, tax- and estate-planning tools and worksheets at its Tools and Calculators web page.

The University of Georgia’s Planned Giving Calculator does basic calculations for charitable trusts, gift annuities and pooled-income funds.

Suggest other free software.